Technically, the BCM50 can even go to 112 extensions.
The BCM50 can have up to 2 expansion units, each with 32 digital extensions.
Also, there are 12 digital extensions and 4 analog extensions on the main unit.
Finally, there are 32 IP extensions possible.
That's a total of 112.
Those options are all independent: the number of one type of extension does not interfere with the
possible number of another type.
Of course, putting 112 extensions on a BCM50 would technically work, but it would be a possible mistake. With this setup, it's possible to have at most 16 trunks into the BCM, which may not be enough for over 100 users.
Furthermore, there's no room for expansion later.
Plus there are only 10 voicemail ports.
There may even be other downsides.
(The 16 trunks comprise 12 VOIP trunks and 4 PSTN trunks: either analog trunks on a BCM50 or ISDN2 trunks on a BCM50b).
I looked at that online "BCM Overview" thing; Nortel mentions "44 digital extensions and 30 isdn lines".
They presume that any large system will have an ISDN30 in it, so this restricts the number of digital stations to 44. They seem to not want to bother mentioning analog extensions, which most users would use only for faxes/modems anyway. (It's a digital phone system, so it makes sense to not mention the analog extensions.)
Having said all that, though, I estimate a BCM450 solution with 32 IP, 112 Digital, 12 VOIP, 2 ISDN would be about 20% dearer than the BCM50. But at least there's much more room for expansion of all of those things.