You cannot register the same dspfarm profile to multiple clusters at the same time, you can build multiple dspfarm profile and have them registered to different CUCM clusters though. Here is a good description:
DSP Farm Profiles
DSP-farm profiles are created to allocate DSP-farm resources. Under the profile you select the service type (conference, transcode, MTP), associate an application, and specify service-specific parameters such as codecs and maximum number of sessions. A DSP-farm profile allows you to group DSP resources based on the service type. Applications associated with the profile, such as SCCP, can use the resources allocated under the profile. You can configure multiple profiles for the same service, each of which can register with one Cisco Unified Communications Manager group. The profile ID and service type uniquely identify a profile, allowing the profile to uniquely map to a Cisco Unified Communications Manager group that contains a single pool of Cisco Unified Communications Manager servers.
from:
http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/interop/intcnf2.html
HTH,
Chris