As HH has said, with it just being the EoI stage of the process, there are no clues via Company House as to who will chuck there hat into the ring.
I think however and thanks to the struggles the DfT have had in general - just to get companies to bid, they'll be max of 3/4 bidders being:
1: Arriva, who as the incumbent will probably know it's vital for there strategy to hold on to the Franchise;
2: Go-Ahead, (including Keolis) who may feel that there time on SouthEastern to current and on West Midlands until last year, gives them a reasonable shout at winning;
3: the Abellio/Japanese consortium who have 2 franchises atm (as well in the mix for SouthEastern) and there is no doubt feel that the experience of Asian companies would help;
and 4: MTR/Guangshen who have extremely deep pockets are probs looking at XC, as a way of maybe linking it into West Coast Partnership in the way Virgin did; providing the Chinese firms win WCP, of which at the moment is widely expected.
First are nowhere in a position to bid, if the Telegraph story of Trenitalia taking over there Rail Divisions from yesterday turns out to be accurate and seeing that Virgin's company that ran XC between 1997-2007 dissolved in 2014, along with Stagecoach's problems I again would be surprised if they got involved. Surely Sir Richard would wise not to, considering the huge mess there partners left ICEC in financially!