Although this topic has been raised on many on occasion - and personally I think that 28 day currency is unreasonable (we use 42), my opinion is:
1. The FI will invariably be the Commander and will log PIC.
2. The other pilot will log Pu/t.
Also, I would expect the pilot requiring the check to be charged at the 'dual rate'. Don't like it? Then maintain your currency!
If there was any real commonsense in the JAA, such flights would be PICU/S for the pilot requiring the check and PIC for the FI. But sadly there isn't......