I decided I'd turn this into a sorta roster and see where it goes ;D
As of 12/26/07:
Companies with a Q2B
Engines: 40, 69, 92, 250, 316
Ladders: L3, L4, L28, TL35, TL53, L83, L105, TL111, L129, L131, L135, L138, L154
Special Units: Rescue 3, Rescue 4, Rescue 5, Squad 18
Companies with another mechanical
Engines: 33
Ladders: TL21, L43
Companies with an EQ2B
Ladders: L2, TL7, TL17, L25, L36, TL45, L47, TL114, TL115, L122, TL127, T175
Special Units: Rescue 1, Squad 61, Collapse Rescue 1-4, Satellite 2-6, Hazmat 1, SOC Decon
Thanks to everyone for their input so far!