Interesting, does your MEL indicate that TCAS is a requirement for RVSM?
Just checked my current MEL just to be sure, but again, it says:
Repair interval B, 1 installed, required 0, it needs a placard if inoperative, and for ops: may be inoperative. Note: TCAS system is not a requirement for operation in RVSM airspace.
Now, since we usually only operate within the ECAC airspace that may differ in other areas of the world, and in fact Egypt does allow an inoperative ACAS system, up to 10 days, however, only until a maintenance base is reached, so any return to base would require a repair before flying to Egypt again.
That said, if you file a flight plan below RVSM airspace, did you indicate unable for RVSM in your field 18 on the ATS flight plan? If not, the ATCOs can only see the filed flight level and therefore offer higher level if your type usually does fly higher levels, and if there is capacity available.