As discussed on the mailinglist, the service API input tags for transaction ids do not support the new 48 bit transaction ids (or: they don't have a _64 counterpart).
As posted by Dmitry:
"But it seems that these inputs tags were forgotten re. their longer
counterparts: isc_spb_rpr_commit_trans, isc_spb_rpr_rollback_trans,
isc_spb_rpr_recover_two_phase. Please file a ticket."