very strong interference on the BCCH could force the MS to reselect another cell. And once in the new cell, it might eventually come back to the interfered cell. If cells belong to different LAC, then … LU is performed.
But the amount of interference must be very bad to lead to such a situation.
IMO, the effect of interference on LU is negligible.
T3212 = 4 hours is a standard value, you can increase it a little bit and see the effect. Most probably the effects can only be seen at NSS level : more paging without response.