Merseyrail are looking at dual voltage stock for their hoped/planned service extensions expctd to take place within the replacement rolling stocks lifetime. I'm sure a longer term order for a new fleet can be done if the Valleys order was combined, maybe with the Northern EMU order added in.
There's no mention of dual voltage in the tender that was issued
Merseyside Passenger Transport Executive ("MPTE") is currently considering its options around the replacement of its current fleet of Class 507/508 EMU Rolling Stock. Should it decide to replace the rolling stock following conclusion of its business case process it would be seeking to award a contract for the design, manufacture and supply of in the region of 150-250 third rail electric (750v) vehicles together with spare parts. In connection with the purchase of new vehicles MPTE is also interested to receive proposals relating to the final assembly, testing and commissioning of such vehicles specifically for operation on the Merseyrail Electrics network and for the provision of maintenance facilities appropriate to such vehicles, as well as funding for the purchase of such vehicles by MPTE and the provision of any infrastructure enhancements which would be necessary to facilitate the operation of the new Rolling Stock on the Merseyrail Electrics network