(...new to all this, so I hope this hasn't been covered to death...)

I was hoping to replace the Jetboil (my wife's favorite piece of gear) with something lighter, but I'm concerned about placing beer cans over a fire. They're lined with plastic - and the pasteurizing temps fall well below boiling - so they're not designed to get anywhere near 212F. And I'd guess that the can itself gets quite a bit hotter than the water.

Anyone know anything about this?

I would think that the inner surface of a beer can full of water will be only fractionally above boiling point. I never use my beercan pot for anything other than boiling water, sometimes with pasta but before it is soft it is transferred to a cosy.
I would be interested too if anyone knows whether any beer cans are lined with plastic

by the way I think jetboil could take quite a bit of heavy steel away from its burner surround without loosing effectiveness.

"inner surface of a beer can full of water will be only fractionally above boiling point.

Yeah, fractions of a degree actually.