In my experience, the 30 minute rule is a holdover from the past. There is some literature (forgive me for not quoting exactly) describing process for measuring temperature of units returned to Blood Bank and it only takes approximately 10 minutes for a unit to exceed storage temperature maximum of 6C. We measure the temperature of any unit returned, consider the 'away' time to be transport, and may discard the unit if temperature exceeds 10C.
Issued units must have transfusion started without delay - the transfusionist is expected to have already obtained consent, have IV access and be ready to transfuse when the blood arrives at the patient's bedside. If there is an unexpected problem (can't find the consent, IV infiltration, etc...), blood must be returned immediately and the unit temperature is measured ; it may be reissued for transfusion within 4 hours of the original issue time to that patient only. If that condition cannot be corrected, the unit is discarded if out of temperature, unspiked, and meets other return criteria established by AABB.