[MrObvious]

Odele. I'm not 100% sure on everything in here but I know a few things:

*They are accurate based on the power of the radio at the time. Believe it or not 100% of the full power allotted the radio isn't used all the time which is why you can have better battery life in a better reception area.
*The PRL isn't causing the battery to drain. It is just essentially a text file saying which groups of towers you are native to and which ones you roam off of. If you are in a crappy area and there is say a Verizon tower where you need Sprint service, Sprint may not let you roam because they don't have an agreement on the particular tower or group of towers. Verizon doesn't roam much to begin with and charges a lot for other carriers to roam off of them.
*The bars are slightly accurate in whether you have signal or not (1 bar versus 0) but you can be right under a tower and not have full bars. This is because your phone isn't using all it's radio power.