Luftfahrt Bundesamt - Homepage - Hubschrauber mit zwei Piloten MP(H)
That's the official point of view regarding SPH / MPH. Of course you can do MPH checkflights on Bo105 or EC135. But since they are not MPH by certification, you will only be able to fly and log Co times on these if the operators manual specifies MPH operations. Usually for IFR / VFR Night.
If the ops manual specifies certain ops as MPH, the PIC needs an ATPL(H) and the Co CPL(H) + ATPL(H) theory + MCC. (That's according to the LBA. I can't find where it says ATPL theory in the regs. - CPL(H) + MCC should do.)
Holm- und Rippenbruch!
Rotatohead