I have come to understand that the autonomous Finnish Orthodox Church celebrates Easter at the same time as Western Churches.
Who made the decisions, and was the Ecumenical Patriarch involved?
Who made the decision that the autonomous Finnish Orthodox Church could celebrate Easter at the same time as Western Churches and was the Ecumenical Patriarch involved?
The decision for this extraordinary move on the part of the Orthodox Churches was primarily made by the Patriarch Tikhon of Moscow. Patriarch Tikhon granted permission for the Finnish Orthodox Church to celebrate Easter with the usage of the Gregorian calendar in October 1921. Although it was Patriarch Tikhon's decision, the Ecumenical Patriarch Germanos did have some input into to the decision.
As for the Orthodox Church in Estonia, it was the Ecumenical Patriarch Germanos who issued the tomos of autonomy on June 7, 1923. Similarly the Patriarch of Moscow was involved in this decicion as well.
The following article explains the situation for both Orthodox Churches quite well: The Date of Orthodox Easter in Finland and Estonia.