Probably but it all depends on what the terms of the license they already have with the TOC. They are all different.
It's very unlikely any license would say "DTG can make our train or route in any game they make, forever"
It is probably down to individual cases, but I expect there are at least a few that let them make DLC for both games. I'd say the DB license would be one of them, but we can't be sure until we get actual confirmation. Likely most of them have two separate deals for both games.
Probably as many variants as DTG have licenses. In some cases, the license may well be per route and not per game. And for all I know, somebody may have said "Our deal was for TSW1; TSW2 is a new product and isn't covered." Now, in some cases (DB, UP, probably CSX), the licensors were happy with their TS arrangement and probably amenable to saying "That deal is fine, we'll just do the same with the new one." Others, however, may have been less satisfied and been more like "We aren't very happy with that TS thing, so the new deal is going to be different." Or even "Not again. Burned once." There are also the cases (e.g. Virgin Trains) where the deal was only valid so long as they continued to operate the route in question. And it might be the case that some licenses are not tied to a particular product, but are time-delimited (OK, you can have a license for five years."
