A B-Reserve who is assigned a trip which reports by 0129 has to be released to a legal rest period by 5:30 a.m. if not given a full legal rest period prior to showtime. The scenario described in the original post if given 8 hours off prior to show may be legal but certainly violates the intent of the contract.

Section 25.M
f. A reserve pilot who departs his domicile to operate a domestic duty period shall be scheduled for release to a legal rest period not later than 4 hours after the end of his RP. This paragraph shall not apply:
i. to a pilot who is released for a legal rest period prior to the showtime of his reserve assignment; or
ii. if the reserve pilot is assigned to a duty period consisting exclusively of deadhead.