There is no definition of what a member of the public is within the PL laws, thus creating a rather neat (and immoral) loophole that civilians may choose to make use of.
An LEO is only so when employed by the city, they do not have (yet) any off duty powers, so that makes them civilians rather than "warranted" officers, meaning that there is no distinguishing between the legal status "regular" civilians and police officers, other than the fact that police officers have the powers under section 11. Since there is no exemptions made in this section, it is perfectly possible in my eyes for a civilian to detain (NOT ARREST) a police officer until a supervisor can arrive.
EDIT: It's worth mentioning that their detention would have to be lawful too, otherwise the officer could arrest them for unlawful detainment. The detainment MUST be to stop them from committing a crime.