"" So if you buy an a/c that had the engine overhaul by A& P , you will have to have the engine overhaul again here in Canada regarless of the hours on the engine..""
That isn't quite true but there are some items related to an engine overhaul that need to be done by an FAA repair station, equivalent of an AMO. This from my TC maintenance inspector:
That the overhaul be documented well enough to determine if the overhaul meets manufacturers requirements as published in their overhaul manual. Also if the work is specialized maintenance it is required to be done at an AMO (in the US it would be accomplished at an appropriately rated FAA repair station). example Lycoming O-320 can be overhauled by an A&P but if the cases are welded or NDT is performed those parts need to be subbed out to an FAA repair station. If you are talking about a radial engine with a 2 part crankshaft it needs to be performed by an FAA repair station. Please See CAR 571 for definition of specialized maintenance.
Part V - Subpart 71 - Aircraft Maintenance Requirements - Transport Canada
Engine
2. Any of the following types of tasks is engine specialized maintenance:
(amended 2003/06/01;
previous version)
(a) the reassembly of a multi-part engine crankshaft or a crankshaft equipped with a dynamic counterweight system;
(b) the reassembly of the crankcase of a reciprocating engine that is equipped with an integral supercharger or a propeller reduction gear;
(c) the overhaul of a reciprocating engine that is equipped with an integral or turbo supercharger; and
(d) the overhaul of a turbine engine or turbine engine module.
Part V - Airworthiness - Transport Canada