TYTEL,
The MiVoice Office 250 will only support 250 phantoms regardless of whether you have a base system or a PS-1. Now, that is if you don't go into Metadata and change it, but that is not supported by Mitel. This also means that you can only have 250 Hot Desk users as well since those are shared with the phantoms, but what we did find out is that you can create more Hot Desk users by making some desktop users and turning them into Hot Desk users, but that isn't supported either; go figure.
In case you were wondering some other odd limits are that the base system only supports 100 Unified Messaging users and with a PS-1 it will support 250 Unified Messaging users. Now, that doesn't mean mailboxes as you can have somewhere around 10,000 of those, this is just the E-Mail Synchronization users that are limited.
Thanks,
TE