SQL Server Service Broker Compatability across versions?
The answer is yes, you can do cross SQL Server versions service broker as long as all instances are 2005 or newer, and only one of the instances can be SQL Server Express Edition.

Here are some helpful links:
http://blogs.msdn.com/b/stuartpa/archive/2005/07/25/443229.aspx
http://msdn.microsoft.com/en-us/library/bb839483(v=sql.105).aspx