That didn't answer my question of how the mark2s could be used, but is still a valid point. As far as I know there are six mark2s painted in the Gerald livery. 3 of these are used on Gerald, the other three I presume are used on Gerald when the first rake requires maintenance. All six have been formed into a single train for Holyhead - Cardiff rugex in the past.
Assuming 2 or 3 rakes of mark3 carriages appear to enable ATW to start using the DVTs, the six serviceable mark2s will be spare. It is possible that the two mark3 buffet cars will also be spare, but that depends if the new mark3 rakes include their own buffet cars or the existing ones get the DVT-67 through-wiring. Anyone know if the plan is to replace the current buffet vehicles or fit them with the necessary wiring?
There are also the stored mark2s, which bring ATW's total to either 18 or 22 (5 BSOs and 13 TSOs if the 18 vehicle count is used, of which 2 BSOs and 4 TSOs are painted in Gerald livery and are actually used). Granted the stored mark2s might not be fit for use, but they haven't been stored for as long as some other stock has and should therefore be relativly easy to refurbish back into operable condition. Given ATW need more stock, and there's no prospect of any DMU cascades for a few years, refurbishing those mark2s would be helpful if we can find a solution to the run-round problem. Does it have to be top&tail 37s or is there any route where conventional LHCS operation with run-round could work on ATW?
But it isn't ending soon is it? According to wikipedia it ends 31st December 2018, so we are stuck with ATW for about another 6 years. ATW will have real trouble running their services this summer if they don't suprise everyone by getting the DVTs into service early to release the WAG2 175, even then being down a 175 (002) and a 158 (being refurbished) will make it difficult. Their plans might just be possible if they had those three extra units, but alot of 158 services would still be reduced to 150s.