I assume that you have read the notes on the ISI web site.
A PIP is obliged to consider BIK. In practice, BIK is not a big issue. For example, a single man without a car is allowed Reasonable Living Expenses ("RLE's") of €938.14 a month. If the needs needs a car, he is allowed an extra €112.34 to cover the costs of the car. If the man is provided with a car by his employer, then the PIP should make an adjustment for how much the man has to contribute towards the running costs of the car.
If the man is provided with a "low interest" mortgage on his home by his employer which attracts BIK, the PIP is unlikely to make any adjustment to his RLE's, as the monthly mortgage payment would provide for the low interest rate.
If the man was provided with free accommodation by his employer, he would not be provided an allowance for rent etc.
The whole purpose of RLEs is to provide a reasonable standard of living to the debtor. The PIP has to be fair to both the debtor and the creditors in deciding the level of RLE's.
Jim Stafford