hi,
this makes for interesting reading, and its unfortunate that you are having these problems. as a tech it sounds to me very much like a immobilizer problem and these problems are usually caused by faulty antenna rings or the keys themselves or sometimes by interference from other sources.
if the problem should occur again remove the key from ignition exit the vehicle lock the car then unlock and try again (this makes the immobilizer perform a new reading on the key).
however anytime you have this problem a dtc (trouble code) should be set inside one of the contol modules which a dealer could then read.
if you have no luck with your local dealer give volvo a ring direct and complain loudly - then they will get onto your dealer (trust me on this...).
as for the whole dealer and warrenty situation,while a vehile is under warrenty it will be fixed so you have no problems and nothing to pay that is the whole point of warrenty BUT as a customer who is not paying for the repairs then you have no say over what is or is not done,if you want to request something specific done then you can but you would have to pay for it.
also dealers dont care about putting parts onto your car when in the warrenty period ,why should they? they get payed from volvo and if anything it helps the parts department meet sales targets and provides work for the service department.
i know there are some dealerships out there that do crap diagnostics and this results in a lot of new parts being fitted to cars,but sometimes elimination of a part is the only way to solve a complicated problem and once a part is fitted it cant be sent back so someone (usually customer if out of warrenty) ends up paying.
hope this helps shed some light,and good luck with your problem.

steve.