Governor's Telehealth Coverage Executive Order, March 15, 2020: PDF at mass.gov. Crucial text from the Order:

[Payers] are hereby required to allow all in-network providers to deliver clinically approrpriate, medically necessary covered service to members via telehealth. […]

[Insurers] shall not impose any specific requirements on the technologies used to deliver telehealth services (including any limitations on audio-only or live video technologies.)

The GIC and all Carriers shall ensure that rates of payment to in-network providers for services delivered via telehealth are not lower than the rates of payment established by the Carrier for services delivered via traditional (i.e., in-person) methods, and shall notify providers of any instructions necessary to facilitate billing for such telehealth services.

MassHealth

BCBSMA - Blue Cross Blue Shield of MA

Optum

Tufts

Aetna

Cigna

Unicare State Indemnity Plan

Medicaid/Medicare

Use location code 02 for telehealth rather than 11 for office (for Aetna, still use 11)
Use modifier GT or 95 for most insurers