The MERV is known as Major Emergency Response Vehicle. Used to be a Mobile ER Vehicle when it was part of the pre-merger EMS, was usually staffed by a MD, where the vehicle was kept.(Queens General,Kings County,Bellevue ER,...) Today manned by 1 EMT. Can treat 8 to 10 laying down pt's and an additional 10 sitting. No DIAGNOSTIC equipment. Just lots of BLS supplies/splints,etc...
The MRTU was not in use when I was in EMS. From what I understand, it is staffed by 1 EMT and repsonds to fires,10-60's,etc... Has several M O2 Tanks, plus lots of "spider ports", they are o2 outlets that can treat up to 4 patients at a time. Lots of monitoring equipment,NRB's,N/C's,etc...
Hope helps.