9 Interworking considerations
22.0913GPPExplicit Call Transfer (ECT) supplementary serviceStage 1TS
The operation of this supplementary service is not affected by the nature of the far end of the connections.
NOTE: In some networks the indication to the remote parties about the invocation of ECT may not be supported.
Annex A (informative):
Deviations of PLMN ECT to the ISDN specifications of ECT