Hello.
I'm affraid it will not gonna work unless you insert another LambdaUnite to decapsulate the GE from teh SONET stream.
I'm not sure how the LambdaUnite is encapsulating the GE but most probably using GFP/LCAS/VCAT or a proprietary method.
In turn I know that the 7200 doesn't know any of the above mentioned protocol.
Hope this help.