Given the potential for there to be three operators between Chicago and St. Louis, station conflicts will arise. At the north end, Union Station is an overcrowded mess. Meanwhile at the other end, Amtrak has partial ownership of Gateway Station (the city of St. Louis is the other owner). Eight years ago when the Missouri legislature was pondering handing its trains over to Herzog, Amtrak threatened to keep Missouri-based trains out of Kansas City Union Station and a temporary St. Louis trailer, and it would have refused to recognize the MO trains as connections to Amtrak trains (go down to the eighth posting [the author was Gene Poon]). Eventually, the Show Me State caved, and all seems to be well between the state and Amtrak now.
Until Florida Governor Rick Scott scuttled his state’s HSR project over two months ago, Amtrak and SNCF were on the same team bidding to operate the route. Now that FL is out of the high speed sweepstakes, all bets are off concerning the two carriers’ cooperation. So, it would not surprise me if upon operation of the two proposed Chicago-St. Louis Express routes, Amtrak decided to keep SNCF and the third operator out of Chicago Union and St. Louis Gateway Stations. When it comes to the Windy City, that would not be such a big deal because 1) SNCF has already proposed O'Hare Airport as a stop and 2) there are other options for intercity service. Even though those are my preference for other operators, a joint MWHSR/Siemens study has proposed its own alternatives for HSR stations in that city which are infinitely better than what MWHSR proposed early last year. In St. Louis, the French operator has already stated a preference for that city's Union Station. Not only can STLUS host SNCF routes, but it can host the other Chicago Express route and a future St. Louis-Kansas City Express route. While it would take some work, restoring the facility for train use should be no problem at all.
Meanwhile out in the Pacific Northwest, there's the possibility that Oregon could reroute the Cascades off of the Union Pacific route and onto the Oregon Electric route between Portland and Eugene or that another operator could use the latter line and compete against the Cascades. The real sticking point would be Portland Union Station. Fortunately, that city owns the facility so it controls who can use Union Station.