PB,
Read JAR-OPS 3.165 (you will find this on the JAA.NL web site); don't even think about making any commitments unless you have first checked with your CAA Assigned Inspector.
AESIR is referring to JAR-OPS 3.165(d) but there are strict limitations attached to this paragraph - it is unlikely that you will find one being used by a Part 135 AOC holder in Europe.
Leasing, even within the EU, is a minefield.
Jim