Aircraft Maintenance Engineer requirements are contained in OTAR Part 66. The requirement to hold a licence is only applicable to those personnel working on an Overseas Territories registered aircraft outside the jurisdiction of an "Option 1" OTAR Part 145 (Aircraft Maintenance Organisation Approval) Organisation. OTAR Part 66 contains detail on the privileges and currency requirements of the licence holder.
Although a formal medical examination is not required, there are requirements for general levels of medical fitness.
Requirements for the validation of a Maintenance Engineer's licence issued by another ICAO contracting state can also be found in OTAR Part 66.