It most likely a loaner just like the one Far Rockaway had during the summer. However, the O5 was on the Q35 going to Rockaway Park this morning (about 11:30AM at the Kings Plaza stop).
More bus transfers:
4430 is at MJQ. I rode it on the M106 (2:10PM Bound to East Harlem) and then on the M96 (3:58PM Bound to West Side).
3747 is at Far Rockaway. It was spotted on the Q21 (6:10PM Bound to Rockaway Park).