Maximum number of tags in BLE RTLS implementation

Hey all, I've been looking into using BLE for RTLS, and I can't seem to find any figures on the maximum number of tags given initial conditions like number of receivers, range, etc.  For instance, if I have four receivers that are all in range of N tags, how big can N actually be?  In theory I think it's unlimited, but clearly there are processing and radio bandwidth considerations, so the number is finite.  I guess what I'm asking is, does anyone have an order of magnitude estimate for this sort of thing in the real world with some established conditions/limitations?  Clearly, part of my problem is that I don't quite know how to talk about the types of conditions that might serve as parameters for this sort of system :-P  Anyway, thanks for any input you might have!