The EASA continuation of approval needs to occur in accordance with 145.B.30 of the regulations. There is no regulatory stipulation requiring a continuation letter and the User Guide for Foreign Part 145 approvals has been updated (UG.CAO.00006-004) on 22/10/15 specifying that the approval is valid for an unlimited duration (for foreign Part 145 approvals) under the provision of 145.A.90, and EASA is not issuing any formal continuation communication to the relevant maintenance organization. Please also see the last paragraph in the attachment (Part 145 release and publication of the new CAO procedures) to this effect.
Please let me know if you have any questions.
Regards,