Integrating SIP / Voip Intercoms?

Looking for some advice, lessons learned and general knowledge on the topic.

Currently our intercoms are routed to a central station, where we use dedicates PCs and software for a little over 100 door stations from 20 sites. Over the next 5 years, we're planning to tripling the number of sites we monitor and looking to tie the intercoms to our CCTV and ACS systems to streamline workflow, namely someone presses an intercom in the field and the corresponding video feed and door release pop-up.

Now I know vendors already tout this capability, but few seem to be with native "tight" integration to IP intercoms and further limited unless you're willing to go end-to-end the same vendors hardware and software. From what I understand additional infrastructure is required to go SIP and you're essentially making the door stations VoIP phones.

This is completely new territory for me, don't currently use VoIP at my company, not even sure if the PBX's have the capability.

If you know anything on the topic or have done this, ALL feedback is welcome; of particular interest:

- What infrastructure is required to connect the site to the SOC?

- Ballpark cost of SIP infrastructure at the site (upstream from IP door stations)?

- Was it worth it in the end? (ie did you save time,money or improve service delivery?)

- Lessons learned?

- Companies to look at?

Thanks all!

Genetec has the best SIP intercom/video/access control unification that I have seen so far. I would be interested to see if anyone else does it better.

Stentofon has the best audio quality IMHO