ChuckB73,
What type of connection are you going to use for this; T-1/E-1, SIP...?
As acejavelin already stated true intercom dialing can be difficult to emulate, but not impossible, and I also do not know the Toshiba product line so I can't help there.
The thing you have to keep in mind is how many resources you have available to you. The MiVO-250 has the 250 on the end for a reason. You can only have 250 phantom/hotdesk/SIP/IP devices programmed on the system; these will be used for the Toshiba programming if you want to emulate intercom dialing. If you don't mind dialing your outgoing digit prior to their extension then those limits can be ignored for the most part as SIP Trunks and T1/E1 limits are different.
Thanks,
TE