Below is some information extracted from BSS documentation:
“It is possible that an MS using an SDCCH slot may need to perform an inter- or intra-cell handover. This need is calculated by the HDPC algorithms using uplink and downlink measurement reports in the normal way
One important item to note is that the interference band allocated to a channel is still the first criterion in the channel allocation algorithms. A channel from the highest priority carrier matching the requested interference band is allocated to a channel request. Moreover, the channel allocation priority is also a secondary criterion after the existing criteria of channel selection in a Multiband, Concentric Cell, and Extended Range Cell environment. Also the channel allocation priority may not be followed for an emergency call if a channel is allocated from the emergency reserved channel pool.
For interference-based intracell handovers, the channel selection algorithm for a non-hopping cell has been modified to consider the channel allocation priority as follows:
Compile a list A with any channels in the best interference band.
From list A, select any channels on a carrier other than the current carrier and compile a list B. If none are available, select the best channel from list A.
From list B, select a channel with the best available channel allocation priority.
It should be noted that the previous criterion of preferring BCCH over non-BCCH in step 3 has been replaced by the channel allocation priority”
Hope this help you to clarify.