Full disclosure I’m a Broker that partners with all the major UC and CC players.
Yeah, Nextivas claim to fame is the ability for customers to pick up the phone and reach a IS based support person within four rings. If that’s what you want to do eight times a month lol.
Ring is good and gets better support wise the bigger you are. And yep they’ll do all three on a number. Or if you need more intelligent based routing without wanting to pay for a full blown contact center they can do it with the lite product RingCX.
Hi, we're implementing an enterprise customer that required this from RingCentral and it was the first of it's integration from my understanding but only supported on Poly CCX 700. We now have it up and running perfectly. As far as the integration is concerned, you'll need to generate SIP creds from RC to input into the video intercom (which needs to support SIP). Second, your RC account needs to have "Video Calling Enabled" turned on. Advanced support should be able to do it for you.
For the phones that you have - no idea if it would work or not. I have a phone a T57W I could test with.