Goussat,
No. It is not possible to create a Link between 2 BOMs from different plant, so that when one is updated it will automatically update the other.
Every type of BOM including Functional, Equipment & Material BOMs are assigned to a Plant and the FLoc., Equip. or Material based on the type of BOM. BOM is specific for that Object and is limited to that plant. So, when you update a BOM it will not change the other BOM which is either copied or is a variant of the initial BOM.
Hope that helps!
Thanks.
Wankash.