For their commercial plans, you don't need additional certification to provide telehealth. Typically it's covered at 80% of the regular fee schedule, but presumably it will be paid at 100% due to Gov Baker's orders.
Tufts Health Together is requiring an attestation form signed by the provider in order to do telehealth (per phone call 3/18). Find the form here
For GIC/Navigator/other commercial plans, if OON telehealth isn't covered, you can sign up for Teladoc and have your client sign up as well. You will then be considered in network with Teladoc and will be paid at 80% of the in person rate. (Per phone call 3/18)
Clinicians sign up here
Clients register here
Telemedicine Services Professional Payment Policy