Of course, their antimagic seems to be area-based, and the steam is magic-powered, so...
We really need to do something about their antimagic.
Other than the creation of anti-anti-magic, we're going to have to start murdering their mages in their sleep or or spend a revision making it so you can hand fuel the engines.
I have been proposing antiantimagicmagic(implying that the antiantimagic should be magical...)...
That, and everyone is allergic to doing any sort of research on the precise effects that their antimagic is having on our stuff. It should be dead-easy to see if it can dispel crystals while wielded by someone with an antimagic charm. If our antimagic absorbs theirs and prevents it from operating within our fields then we will know. Getting a first-hand description of precisely how a wizard's fireball failed would be marvellous. Does it just vanish, does it get sucked away, does it go all wonky and spill everywhere, does 1+1 suddenly equal fat caterpillar? Does it remove our sustained fogs? We can use them to blind the enemy and disrupt their coordination, and do drills to train fighting within fog... if the fog works at all. If sustained magic works then we know it is an instantaneous effect or something that can be countered with persistent magic.
Order: silver cage caltrop delivery method.
make little silver cages, all runic and such, all cosmetic-laden, with a simple knot holding it closed. Fill it with crystal caltrops before a fight and hang it upside-down from a thane with an antimagic charm. If the thane repositions towards the rear, they can pull on the knot, caltrops drop to the ground, someone can witness how long they remain extant. The enemy thinks it is the pointlessly cosmetic baggies protecting them, if it works, if it doesn't then we know that their antimagic is penetrating ours... We only need, like, half-a-dozen of the things to test the theory...
Order: Fog training.Train soldiers to fight within fog. Identify allies and keep track of forwards and backwards and walk on uneven terrain and such. Just a couple of squads for now as proof of concept.