With vMCD there isn't appears to be an option to switch RFC2833 on/off.
I would guess it supports RFC2833 by default, however you only have the option to manipulate KPML with vMCD.
I can't tell for physical deployments as I run vurtuals across the board.
Here is your RFC support:
RFC Support
SIP Trunking for 3300 ICP Release 6.0 is based on the following specifications.
RFC1321 - The MD5 Message-Digest Algorithm
RFC2617 - HTTP Authentication draft
RFC2782 - A DNS RR for specifying the location of services (DNS SRV)
All Srv RR received are ordered jointly by priority and weight. For simplicity, the current implementation does not support server load balance information conveyed through the change of weight in SRV RR.
RFC2833 - RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals
RFC2976 - SIP INFO Method
RFC3261 - SIP Session Initiation Protocol
The 3300 ICP operates as a Back-to-Back User Agent.
It supports UDP, TCP, TLS transports.
Both SIP-URIs and TEL-URIs are accepted on incoming calls although only SIP-URI's are used for outbound calls.
The Options method used for link management.
The configuration allows for Outbound Proxy Servers.
Sending REGISTER messages is supported but incoming requests for registration are not.
RFC3262 - Reliability of Provisional Responses in Session Initiation Protocol
RFC3263 - Session Initiation Protocol (SIP): Locating SIP Servers
Does not interpret " regexp" provisioned in NAPTR RR.
RFC3264 - An Offer/Answer model with SIP
RFC3265 - SIP-Specific Event Notification
RFC3311 - SIP UPDATE Method
RFC3323 - A Privacy Mechanism for the Session Initiation Protocol (SIP)
RFC3325 - Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks
Configuration allows for sending of P-Asserted-Identity and use of the Privacy header when privacy is requested.
RFC 3326 The Reason Header Field for the Session Initiation Protocol (SIP)
RFC3515 - The Session Initiation Protocol (SIP) Refer Method
REFER may be received by the 3300 but will not be generated
RFC3725 - Best Current Practices for Third Party Call Control (3pcc) in the Session Initiation Protocol (SIP)
RFC3824 - Using E.164 numbers with the Session Initiation Protocol (SIP)
RFC3891 - The Session Initiation Protocol (SIP) "Replaces" Header
RFC3892 - The Session Initiation Protocol (SIP) Referred-By Mechanism
RFC3966 - The Tel URI for Telephone Numbers
RFC4028 - Session Timers in the Session Initiation Protocol
Partial support, Session Timer is configurable.
RFC4244 - History Info
RFC4566 - Session Description Protocol
Supports G.711 A-law, µ-law, G.729a
RFC4730 - SIP Event Package for Key Press Stimulus (KPML)
RFC4904 - Representing Trunk Groups in tel/sip Uniform Resources Identifiers (URIs)
RFC4916 - Connected Identity in the Session Initiation Protocol
RFC5079 Rejecting Anonymous Requests in the Session Initiation Protocol (SIP)
RFC5806 - Diversion Indication in SIP
RFC5876 - Updates to Asserted Identity in the Session Initiation Protocol
RFC6140 Registration for Multiple Phone Numbers in the Session Initiation Protocol (SIP)