The Network Rail deal is different and not dependent on another union?
TSSA represents rail staff and some managers and my understanding is that TSSA is conducting an e-vote for members that aren't managers, so the rail staff deal can be signed off and people paid. Managers will then be dealt with separately later.
The TSSA vote ends October 4th so the result will be available almost immediately, and then the TOCs can proceed. However, it seems the RMT has asked if the TOCs can consider accepting the deal before the TSSA result, which seems unlikely just in case TSSA members all decide to vote no...