However, aircraft need to have a TCAS system these days and this makes it difficult. It goes down to ATA 34-40 and some CAA have superseded the MMEL of some manufacturers to have the AOC MEL showing that RVSM compliance is only given if an operational TCAS system is available.
I think you are slightly confused her as to what the MMEL of a specific aircraft is. It is an agreement between a cival authority and the manufacturer.
JAA | Master Minimum Equipment List - MMEL
Here is a great reference to current MMEL's, it will show how vague they are written. A carrier requires a MEL to be written and approved by a civial aviation authority to be in compliance with their ops spec for a given fleet. A carrier can decide to add RVSM notes to an MEL but do not need to even in required components for RVSM if the authority decides the carrier has covered the requirement through other means.
RVSM is maintained to IACO standards, the global aviation authorities establish these requirements so that they are the same (as close as possible) internationally.
TCAS in my oppinion has nothing to do with RVSM. Altitude maintaince is the main focus.