Southside
Yes, many officers have been arrested by the service police. It just isn't well publicised.
Champers
As you might imagine, I have to disagree with you.
Service personnel serving overseas are only subject to UK criminal laws by virtue of the fact such laws are incorporated into the service discipline acts (eg AFA 1955). It is from the service discipline acts that service policemen abroad derive their powers of arrest.
The wording on warrant cards makes no mention regarding powers of arrest. The warrant card explanation you cite is legally dubious and has never been challenged in the courts. If it were so conclusive, why would the sponsors of the new Armed Forces Bill (who would have consulted, amongst others, service lawyers) have gone to the trouble of re-wording the arrest provisions, in order to give service policemen a power they already possess?
You may well have seen arrested officers, but how do you know they were not arrested under the ordinary criminal law or that the arresting policeman had not spoken to a provost officer beforehand? There is no requirement to 'call out' a provost officer in order to obtain his order to arrest. A telephone call would suffice.