Ross's infinite intensity and crossfit oughta get things going on the conditioning end, but it can always be made more specific and with a goal like firefighting in mind I think you can definitely make some good additions here and there. You're still going to be dead at the end of the day no matter what you do, but some specific conditioning drills may help you do the job better (which should be the goal anyways right?)
I like sled drags with an out of service fire hose. I have 125 feet to move and with a 50 foot hose attatched to my sled, that gives me a 75 foot sprint followed by a 50 foot hand over hand pull. shoot for 10 sets done on a repeating 2 minute repeating timer (so work+rest = 2 minutes). Go ahead, load your sled up to 100 lbs and give it a shot. For those who won't buy a sled (like me) I offer this alternative:
Here's how the eye is attatched:
Sandbag work. Make a sandbag, shoulder it 50 times (25 to each shoulder) in 20 minutes. If you can accomplish that, repeat next week with more weight. IRL you almost NEVER have to firefighter carry an unconscious victim (at least I've always been tought extremity carries and drags work better and won't throw out your back) but getting used to moving around dead, unstable weight will only help you. you can also use your sandbag for carries (bear hug style, zercher style, firefighter cary style, etc.) which brings me to...
Farmer's walks! Love these things. By all means, make your own handles (or buy a pair Mr. Fancy Pants) and you can use the same rep scheme as a I do with sled drags (100ft walks every 2 minutes). Its a total body exercise that will kick your ass... as far as specificity is concerned though, maybe not so important. However...
Sledgehamer swings bring a lot to the table. Asside from actually mimicking swinging an axe, beating a tire with a large sledge will hit your grip a lot harder than you expect. I like this as a finisher at the end of my conditioning work, most swings I can do in 5 minutes should do the trick. Or as its own session, sets of 50 swings (overhead or diagonal) alternating hand positions every 5 swings with 1 minute rests wouldn't be a bad way to go. I like a heavy sledge (a 20lb does the trick for me) but lighter sledges do have their purposes too. I may make an adjustable sledge in the near future just so I can have a pic to demonstrate how to do it, but generally you can buy what you need and adjustability isn't normally an issue. While you have that big tire though....
how about doing some tire flips! flipping a 600 lb tire is a great workout and on occasion you may find yourself in a position where you have to move an object in much the same fashion you would flip this beast (pushing into the tire insteat of lifting up). Another good finisher or good as part of a medley (50 sledge swings, 4 tire flips, etc., repeat).
All in all what you've got to look at is what fatigues you the most and train to do that. Bear crawls with a harness attached to the sled (or even without it) to mimic crawling through a smokey house, hill sprints (with a sandbag if you're a stud) or stair running to get used to going up highrise stairs, etc. Figure out what fatigues you and spend some time practing it. That's all there is to it.
As far as a lifting plan, much to my dismay, you need conditioning a lot more than you need heavy weights, so I limit my weightlifting to 2 sessions per week (not including grip training which I do as a hobby up to 4 times a week) with an emphasis mostly on peak strength (an exception made for a 20 rep overhead squat goal of mine). I would like to post glowing results from methods like complex training and whatnot, but I haven't had the discipline to stick with them long enough to yeild results. I lift heavy things, strive for progress every week (change things when I don't get it) and by and large I go home happy. I'll some day return to the allure of complex training, but for now, I'm good with heavy shit.
Hope that helps! I think Mike's right though: Fires will fatigue you no matter how hard you train, but good training will help and improve performance. Good luck!