I believe that what Jandre calls MVS came about in the US when the Big Imaging Companies (
eg, G.E.*) started to maintain not only their own equipment, but others (
eg, Philips*) as well.
Smaller players found straight away that they were kept out of the game by "difficulties" in procuring parts from the Big Imaging Companies.
Later on, the MVS model was extended to non-imaging equipment as well.
But "Multi-Vendor" is not new. O&M contractors (in Saudi Arabia, for example) have been doing it for donkey's years, as have ISO's (Independent Service Organisations - third-party maintenance providers, in other words) and hospital management (maintenance) companies all over the world.
As I say, MVS was distinguished from ISO by the fact that the ISO's couldn't get imaging parts (and tech info,
etc.) easily. That situation continues in varying degrees to the present day. In short, some OEM's like to hang on to service revenue. So (when discussing the possibility of bringing on board an MES or MVS contractor), wise hospital management should enquire how original parts are to be sourced. One answer there might be for the hospital to obtain parts themselves then hand them over to the contractor.

*
Other Big Imaging Companies are available!