The announcement came over the transom in summer 2005: A company going by the name of Connex had acquired transit carrier ATC, and in the process had become the largest private transportation company in the United States. The coronation came rapidly and quietly, a remarkable ascendancy for a company that didn't even have a U.S. presence prior to 2001.

Connex is now Veolia Transportation, itself a subsidiary of the sprawling Paris-based Veolia, a conglomerate with hands in energy, waste services and water, in addition to transit. A known commodity in European markets, Veolia, in short order, won commuter rail, paratransit and bus contracts on the East Coast, West Coast and points in between. Over the same period, Veolia gobbled up regional transit services -- Yellow Transportation of Baltimore (its first U.S. acquisition, in 2001), ATC, SuperShuttle, Kansas City Transportation Group, ShuttlePort Holdings LLC and more.

And now, with the purchase of the largest private taxi and shuttle service in the region, Pittsburgh Transportation Group, Veolia has gained a toehold here. The deal, signed in January, was revealed last week and is being reviewed by the Public Utility Commission.

"They liked our footprint," said Pittsburgh Transportation President Jamie Campolongo in an interview last week. His company operates Yellow Cab, Peoples Cab, Checker Cab and various limousine and para-transit shuttle services, making it the region's largest privately held transportation group.

Veolia's rapid growth means a large and still-growing part of America's urban transit infrastructure is either owned or operated by a foreign-owned company.

So how did they do it without anyone noticing? By sticking to smaller acquisitions and short-term contracts -- big sexy deals, after all, stir up big sexy controversies. When Indiana's turnpike and the Chicago Skyway were turned over to foreign investors, Australia's Macquarie Bank Ltd. and Spain's Cintra Concesiones, protests came flying -- not just over the nationalities of the investors and the notion that we should have to pay foreign banks for the privilege of driving over American highways, but also over the duration of the deals (99 years in the case of the Skyway, 75 years in Indiana).

And in 2006, a congressional election year, the controversy kicked up by the Bush administration's plan to allow the United Arab Emirates to manage six major U.S. ports was so fierce that Dubai Ports World abandoned its management bid.

"I see it as really a kind of jingoism, and people not coming to grips with the global economy," said Bob Poole, director of transportation studies for the Reason Foundation.

All the while, Veolia was building a roster of clients and acquisitions -- more than 120 North American locations, moving 500 million North American transit passengers every year.

"It's the privatization trend that has been going on for 20 or 30 years," Mr. Poole said.

Veolia's transportation arm traces its roots through Connex back to a French railway company that began operations in 1968. Since 1980, Connex has been a part of the Veolia water-waste-environment conglomerate, which sees growth potential in the United States beyond transit. In fact, Water North America Operating Services already has broken into Pittsburgh, winning a contract to operate the Elizabeth Township Sanitary Authority's sewage plant. It also sees growth in privatizing water services, though Americans have been wary of foreign takeovers of water systems.

On the transportation side, Veolia's big break might have come when it ended the Amtrak headlock on U.S. intercity rail travel, winning a contract in 2003 to run Boston's commuter rail network. From Boston and the Virginia-Maryland Beltway, it chugged westward to Denver, Texas, Phoenix and Los Angeles, the last of which also was formerly served by Amtrak.

America was ripe for transit infrastructure investment because "Europe is at least 20 years ahead in terms of public transportation, high-speed rail, its bus systems," said Mark L. Joseph, CEO and vice chairman with Veolia Transportation. In a sprawling country that has built itself over the last century on the premises of auto travel and cheap gas, "we have to make it attractive for people to get out of their cars, [recruiting] nontraditional public transportation users," he said.

As it expanded in North America, Veolia has hit a few rough patches abroad -- it was stripped of two rail contracts and a bus contract in London, after passenger complaints about poor service and late buses. And in Australia this year, Veolia was hit with record fines -- $15 million -- for late trains and trams.

For now, Veolia Transportation does most of its business in "fixed route" services -- trains and buses, in other words. But it sees big growth potential among customers who would rather not wait for the bus or train -- so-called "on demand" services, taxis and airport shuttles that pick you up at your house, for example.

The Pittsburgh acquisition (which is being formally protested through the state PUC by Pittsburgh's Pettus Taxi Service) fits nicely into that growth strategy.

But might Veolia be angling, someday, for a larger share of the Pittsburgh market? Say, the Port Authority of Allegheny County?

A study commissioned by Allegheny County Chief Executive Dan Onorato said the Port Authority, if it is to grow in the future, might have to explore public-private partnerships.

But when the Pennsylvania Funding and Reform Commission (a panel investigating how the state should best fund transit and road and bridge repairs) invited Veolia Vice President Ron Hartman to talk about a private-public partnership, he said Veolia (then Connex) steered clear of transit "systems with unstable funding."

The Port Authority funds its system with user fares and subsidies, including a controversial tax on alcoholic drinks poured in taverns and restaurants in Allegheny County. That tax is being challenged in court.

The year-to-year instability doesn't mean Veolia would rule out a partnership, said Mr. Joseph, Veolia's CEO.

"We are very excited about Pittsburgh as a market," he said. "We hope to partner with the transit authority to look for investment in rail," or other transit services, "bringing not only capital but operating expertise" to Pittsburgh.