If there is only Rx feeder swap between two cells you will suffer of high number of dropped calls and HO failures due to weak UL (the cell is running without diversity). You can check also the path ballance of the cell.
If there is Tx feeders swap the HO performance will be low, due to incorect BA list. You can chech it by the HO statistics. If the best NB of cell A is cell B, but the most outgoin HOs are to cell C which is in another direction, it is possible to be due to feeder swap.