There are two considerations here; licensing requirements and operational requirements. In the UK these are dealt with by two separate departments within the CAA, each with its own agenda. Consequently, the UK's interpretation of the requirements may not be the same elsewhere in Europe. Bear in mind also that, since the UK has implemented JAR-FCL 2 only to amendment 3, the definition of a multi-pilot helicopter depends solely on its certification - the inclusion of operating status in the definition happened at amendment 4.
Licensing Requirements (JAR-FCL 2) - There is only one type rating per helicopter type - i.e. there is no such thing as a MP type rating or an SP type rating. If a type rating course and LST is conducted in a single-pilot environment, an unrestricted type rating is issued, if training and testing is conducted in a multi-pilot environment, the same type rating is issued but restricted to multi-pilot operations. This restriction may subsequently be removed by undergoing a SP LPC. If, subsequent to the issue of an unrestricted type rating, the holder undertakes a MP LPC, the rating becomes restricted to multi-pilot operations. No rating is restricted to SP operations (i.e. an unrestricted type rating allows the holder to act in any capacity in either SP or MP environments).
Operational Requirements (JAR-OPS 3) - Flight crew operating under JAR-OPS 3 must undertake an Operator Conversion Course, which may be combined with type rating training; however, if a type rating is already held, only the OCC is required. This conversion course syllabus includes elements of CRM training but not MCC. Assuming that the conversion course and, subsequently, a combined OPC/LPC is conducted MP then the type rating is restricted to MP operations only. An unrestricted type rating may, however, be maintained by completing certain extra items in the LPC as SP.
MCC training is a pre-requisite only for the first multi-pilot type rating. Since, in the UK, this currently depends only upon the aircraft's certification, it is a requirement only for aircraft such as the S92. So far as the UK is concerned, the AW139, S76, SA365, etc. are, at present, for licensing purposes at least, single pilot helicopters, irrespective of the role in which they are employed and MCC is, therefore, not a pre-requisite. Neither is MCC training a requirement of JAR-OPS 3 and so it is perfectly possible for a pilot to operate in a MP environment, either as PIC or co-pilot, without ever having completed MCC training, although he will have completed the Company's CRM training.