This is a very interesting agreement. It lends credence to those who said that DART was holding up the negotiations. Why? Because *the T* will pay TRE for any incremental costs of the Amtrak service, and for any performance penalties assessed by Amtrak, and for Amtrak's additional insurance costs (required because of the state liability cap which covers DART & TRE). DART won't pay anything. (TRE is a joint project of DART and "the T".)
This will unlock DART's federal ARRA grant to double track from Centrepoint through West Irving stations (the "Valley View Road" area).
Apparently, according to the rumor mill, UP was annoyed by the delay, and told the T that they wouldn't authorize the TEXRail project until Amtrak moved to TRE. So this should gain UP's approval of TEXRail. (TEXRail needs to parallel UP within UP right-of-way for a short distance to get from the Fort Worth station onto the Cotton Belt route; it's not long, but it's a critical section.) TEXRail is going to run high-floor equipment, which will require some new high-level platforms at both of the existing Fort Worth stations.
Apparently the agreement still requires the concurrence of Dallas Garland & Northeastern Railroad, but since they're a short line they'll probably agree (they are pretty much totally dependent on the good graces of everyone else involved in the deal).
Other interesting points: TRE can shut down the line for maintenance for up 20 days per year, whiich must be Sundays and holidays, and Amtrak has to find alternative routes on its own. More days than that, and TRE has to compensate Amtrak.
As for faster Amtrak service: Amtrak is timetabled at 1 hour eastbound Ft. Worth - Dallas, and 1:35 westbound (!!!), presumably due to the Tower 55 moves. TRE is timetabled to take 53 or 54 minutes from Dallas to the ITC, all day long, with lots of stops. Recall that TRE is also locomotive-hauled, so it's just as slow as Amtrak. Amtrak should therefore be able to get a 55-minute schedule in both directions, even if it has to follow a TRE train the whole way; this is probably too generous an allowance, as Amtrak should be able to pass some TRE trains.
There are also 20 minutes scheduled for the Dallas stop in either direction. At Fort Worth, there is a 22 minute stop scheduled eastbound, and 45 minutes (!!!) scheduled westbound. While some time might be desired for recovery time, I would really expect it to be possible to reduce the westbound time to the eastbound time. So eastbounds should have at least a few minutes taken off the schedule, but westbounds should have over an *hour* taken off the schedule (40 minutes between Dallas and Ft. Worth and 23 minutes at Ft. Worth). This is before considering any reductions in time between Ft. Worth and Cleburne thanks to the Tower 55 work.
Amtrak will probably want to reschedule the westbound substantially. The Texas Eagle / Sunset Limited PIP advised a significantly later departure from Chicago as well as a somewhat later arrival in San Antonio. Amtrak wants to minimize the layover time between the Texas Eagle and Sunset Limited. If the Eagle arrives in San Antonio at, say, 11 PM, and over an hour is chopped out of the schedule, it could depart Chicago at 3:45 PM or later. This would put the overnight segment between St. Louis and Little Rock, which is about as good as you can do.
I would expect the train to be moved over on the current schedule first, and a big schedule change to come a bit later, probably accounting for all the Illinois trackwork as well as the changes in Texas.