On the EASA list, the only mandatory MP helicopter is the S92. All others, including the 225, can be flown SP under certain circumstances. In the context of an ATPL skill test, an aircraft is considered to be MP if it is certificated MP in the Flight Manual, or is operated as such by a particular operator.
The EC 135 complies on both counts. Provided that the full LHS instrument panel is installed, the Flight Manual clears the aircraft for MP IFR, and some operators (Bond in the UK) have MP procedures enshrined in their Ops manuals, thereby meeting the alternative requirement.
On my shiny new EASA licence, my EC135 type rating explicitly allows me both SP and MP privileges.
The UK CAA have issued several ATPL(H)s following skill tests conducted by Bond.