Accommodation of devices not purchased from or originally provisioned for service by 8x8 is on a commercially reasonable effort basis. These devices are not guaranteed to be supported on 8x8 service.
Do you have Polycom phones that you would like to reuse with 8x8 service? That’s great! You can reuse existing Polycom phones with 8x8 as long as they are a supported model with a valid factory installed device certificate. It's crucial that Polycom certificates are factory installed and not added later.