This isn't a terribly fair comparison, as BT infantry are horribly, horribly nerfed (rifles only able to shoot 90 meters, and that has a nasty "long range" penalty? Get real). Worse, there is a huge difference between a lance of Stingers and a lance of BattleMasters, though both 3025 designs mount a pair of MGs for anti-infantry work.
Is it the infantry alone, or are they part of a combined arms unit? I'll gladly trade one lance of 'mechs for a company of inferno-SRM-armed infantry in a Battalion vs Battalion fight. I'd rather have 2 companies of 'mechs and a battalion of infantry than three companies of 'mechs, most of the time.
But unless I was guarding something they wanted, I'd pretty much never want to stack up a company of infantry vs a lance of 'mechs. And a properly-armed anti-infantry 'mech can, if the circumstances are wrong, wipe out an entire company of infantry in the course of a single round, which would point to a lance of 'mechs being "equivalent" to an entire battalion of infantry.
The FedSuns RCT setup of 1 'mech = 3 tanks = 5 infantry (platoons) strikes me as reasonable in 3025, if quite disdainful of tanks (give me a 3-on-1 ratio of tanks vs 'mechs on most maps and I'll gladly curb-stomp the 'mechs).
For similar-weight-class 'mechs and vehicles, I'd say 2:3. Infantry don't have weight classes, however, which makes them difficult to judge. It takes a lot of infantry to equal the BV of even a single 3025 Stinger or Vedette, so I don't think BV is a good measuring stick for the PBI.
