Our existing space has about 120 AT&T Centrex lines. Very old school, very cheap to install, very expensive monthly charges, very easy to administer, and the phones work when the power goes out -- which is frequent here. Centrex doesn't have a lot of fancy features, and you pay a lot to add them. We don't need much -- voicemail on about half the lines, a few people need Caller ID, that's about it.
Ideally, we'll add another 120 Centrex lines. Checking with AT&T to see if they have another 120 pairs available here. We're a couple of cable miles from the CO, so I'd be astounded if they pulled more pairs just for us. Last time we added lines here, didn't look like they had a lot more pairs coming into the MPOE, and other tenants have moved into previously-empty spaces since then.
Our only alternative is an Avaya VOIP system. Corporate standard, no other vendors allowed. We'd dump our existing Centrex and go all VOIP, need about 240 lines. Lots of features, sexy new technology, security issues, high up-front cost, high administrative load, need some POTS lines for backup when the power fails.
Still waiting for a quote from our contract, but a pretty good estimate shows the VOIP system will cost about $100K more up front, with a pay back time around 2 years. Regardless of the payback time, I might have a hard fight to get the extra $100K up front.
If we can't get the Centrex lines, the decision is easy.
I'll know more in a few weeks.