Commercial Module: Extension Routing restricts trunks to assigned extensions
I have a customer that leases space to other related businesses in the same building. They do need to call each other, but want to pay their own phone bills, and have their own auto-attendants and message-on-hold. FreePBX works great for this.
One catch in using FreePBX for multi-tenant would be restricting extension to extension dialing, as there is no native partitioning built-in. There are ways to do it, but you need to know what you are doing.
And another issue is you can only have an extension number assigned once, so every tenant would have to use a different extension range.
Take the advice given in this forum.