Hi StarTrekAngel. VoIP: you're right, from the video alone you can only see that they use Polycom and that the touch codes are standard Asterisk - but that could be another VoIP platform - it's impossible to be certain from just watching the video.
I can only speak from my personal experience. Uupon visiting London Bethel I was able to take a look at (1) the server room [yes, a "friend" who worked there showed me into the inner sanctum] and (2) the VoIP handsets in the guest apartment where I stayed. It's Asterisk.
If you want to verify this then simply sign up to a free VoIP service (such as SipGate) and dial the London HQ on +44 (0) 208 906 2211, whilst tracing the call using WireShark. All the info is in the IP packet headers. Of course, it is possible that the London Bethel has not yet migrated over.