The problem is: there is no eclipse resources subsystem available in RCP
platform, so it is not possible to listen for any notifications from the
eclipse resources there.
I really suggest you to regenerate your diagram in NON-RCP mode. This will
simplify a situation and you'll have (I hope) synchronization code generated
by GMF for you.
AFAIU you are using RCP+resources platform to run these diagrams and in this
configuration it really make sense to use non-RCP diagrams.