44.060, 10.4.5, does say ‘The RRBP value specifies a single uplink block in which the mobile station shall transmit either a PACKET CONTROL ACKNOWLEDGEMENT message or a PACCH block to the network. If the RRBP field is received as part of an RLC/MAC block containing an RLC/MAC control block, the mobile station shall transmit a PACKET CONTROL ACKNOWLEDGEMENT message in the uplink radio block specified, except if:
– The received message is a Packet Paging Request, Packet Access Reject, or Packet Queueing Notification message, or
– It is specified elsewere that the mobile station shall not respond to the polling request.’
The ‘specified elsewhere’ part isn’t helpful: it turns the whole thing into ‘you might not get a packet control ack.’ If ‘elsewhere’ was well defined, i.e. if there was a list of control messages that don’t result in a PCA, then this would be simpler.