Symptom:
DTMF to IVR fails , when RFC2833 is negotiated as both sides support it , however Call Manager sends subscribe to endpoint which supports, and it sends DTMF via NOTIFY.   DTMF configuration is best effort/ No preference on SIP Trunk to IVR.

Call from  Agent phone to  IVR negotiates RFC2833 for DTMF relay as both sides support it(No MTP is invoked) , CCM incorrectly sends SUBSCRIBE to the agent phone line side ( as agent supports both NOTIFY/RFC2833)   , and agent sends DTMF digits via NOTIFY .  As MTP was not invoked as both sides negotiated RFC2833, the NOTIFY dtmf digit received by CCM  that needs to be sent to IVR as NTE/RFC2833 cannot be converted to RFC2833/NTE and DTMF digit is dropped.

CallManager  shouldn't subscribe for kpml if 2833 is supported by both endpoints.

Conditions:
There is no MTP and negotiated rfc2833