Can a set of Stronglight JIS track crank arms (107mm axle length) be fitted to my BB (110mm spindle length), or must the axle length of a crank arm match the spindle length of the bottom bracket?
Possibly. If both the bottom bracket and the cranks are JIS, the difference is only 3 millimeters. It will move the cranks 1.5 millimeters outwards. Thus, because the cranks move outwards and not inwards, there would ordinarily not be much danger of the cranks or chainrings touching the chainstays.
However, since the Stronglight JIS crank arms are "track cranks" and your existing cranks may not be "track cranks", it is very possible the Stronglight crank arms have a narrower "Q-factor", i.e. the pedals are closer together. Thus you may possibly run into clearance issues. This depends on whether your frame has been designed for track cranks.
It is the cranks or chainrings touching the chainstays that will ultimately determine whether or not a particular crank fits.