I remember they were planning to have narrower trains than in Rem A. Thought it was in the Techincal Book but cants seem to find it now. That makes the future interoperably not possible. But nothing is set in stone until the contracts get signed. Who knows, maybe the consortium with Alstom will win again.Well I use the term "compatible" loosely here. I know that they won't actually be connected, and technically since REM Est will have 40m long cars, you wouldn't be able to through run in most circumstances, but my point was that it is the exact same technology and very similar build standards. Theoretically if you would connect the tracks up and update the automation, you could would be able to run trains through if you did something about the different platform lengths.