Just called United to upgrade my wife on an upcoming trip booked via United Vacations. I was planning to burn my remaining RPU/GPUs. The reservation shows in united.com as "eligible for CPU". But the agent tells me that it's a "bulk ticket" and thus cannot be upgraded with the RPU/GPU. A case of HUCA? Or a rarely-talked-about fare rule that I of course cannot verify since united.com doesn't show the fare rules for existing tickets?