Yes, it can. Two different ways we did it:
[li]My old company moved to Alexandria, but needed to keep a small office in Arlington. The VP wanted the receptionist able to take calls and route them to employees at both sites. We bought 2 PBXs, one for each site. The main site was a bigger model and had the company’s voice mail unit. The satellite office had a smaller model PBX. They were tied together with TIE lines, leased lines that would seemingly act as direct wires (but with some programming exceptions).[/li]
The main office’s extensions went from 3001 to 3199; the satellite office had 3200-3299. The main PBX was programmed to route 32## extensions through the tie lines, sending a parameter of 2## (the local extension number). The small PBX would then connect the incoming TIE line call to extension 32##. It worked in reverse for the small office calling the main office.
Each office had a set of outside lines so as not to choke each other’s capacity, nor the TIE lines.
[li]Before the above arrangement, we needed to open a cheaper cost center for a new contract. So we rented another suite in the same building, but at a cheaper price. We then had a bundle of wires connected to the patch panel for our main PBX and routed down through holes in the utility closets to our new suite. There, they were attached to another patch panel, which was attached to RJ14 jacks throughout the suite.[/li][/ul]