My understanding is that the 525 is type certified for single pilot or multi pilot, the FAA type rating can be for single pilot or SIC required, I have been told by some AOC 525 pilots that the UK CAA issued them with a MPA type rating!
As far as logging the hours, JAR FCL-1 states: Co-pilot means a pilot operating other than as pilot-in-command of an aircraft for which more than one pilot is required under:
The list of types of aeroplanes (see Appendix 1 to JAR-FCL 1.220) OR
The type certification of the aircraft, OR
The operational regulations under which the flight is conducted.
The 525 type certification requires: one pilot, plus additional equipment as specified in the kind of equipment list OR one pilot and one co-pilot.
With the correct licence and CE525 type rating I think its fairly clear that the hours can be logged and do count as multi crew. I have not found any reference to private or commercial ops in any documents.
An aircraft that has a type certification of only one pilot may also be flown with more than one pilot when the operational regulations under which the flight is conducted require it, i.e. AOC. This is not the same as the 525 and I think this is where the misconception comes from.
However, the CAA will have the final say on the interpretation; I have tried to get written conformation but obviously got referred to LASORS. I am interested to see where this ends up for you as I am in exactly the same situation.
Best of luck.