Eugenio
If we knew a bit more about your environment and about your requirements then we might be able to give better answers. Bridging and source route bridging are operations at layer 2 and since IPSec is to transport layer 3 IP packets it is not possible to do native source route bridging and transport it in IPSec. If you were to configure DLSW between the routers which carries the source route bridging between the routers in IP packets then it should be possible to transport the DLSW using IPSec.
HTH
Rick
HTH
Rick