Ancient aviator - I think you'll find that the only hydraulics near the tyres are the brake lines which have a reduced pressure (2000psi IRC) and have hydraulic fuses that should prevent a leak becoming too large. All the 'big' hydraulics are the other side of the bulkhead. However, the reason we used to carry the extinguishers was was for brake fires - which can become nasty.
Unfortunately, I suspect that the reality is that a big brake/hyd fire would not allow the extinguisher to be got out in time to be much use (it is quite hefty), it wouldn't have been much use even once in position. Furthermore, there may have been a Mayfair Tractor in the way? Who knows - only time will tell.
If however, a fuel leak caused by FOD/bullets/leak and then which caught fire may have been prevented from spreading by the fitting of foam. Again who knows?
Speculation is interesting but it detracts from the main arguments that ESF should have been fitted to this aircraft before it was deployed. Its replacement should also be fitted - but it won't!
Where is the ballistic matting and why are we flying in the day? It all seems a bit unecessary to me.
We are using up our luck at a most alarming rate!
Rust In Pieces XV206