I'm a d20 simpleton, but I've been playing a little bit of MW5 to get a feel for it before I consider playing tabletop.

I saw this video while randomly browsing YT:
https://www.youtube.com/watch?v=KlHDe4KqQ64

Can infantry actually take on larger mechs in this setting? I'm not sure what rifle the guy is using to plink at the warhawk, but I wonder if he actually has a chance at killing it, even if he could consistently hit the cockpit somehow.

I read in the game that an infantry group managed to talk a light mech into surrendering by threatening it with an inferno SRM. I assume that's a javelin sized weapon for infantry, or maybe even full on wheeled artillery. But they probably got it to stop for whatever reason, so that probably doesn't count as actual battle, but just a very lucky trap.