Well in whatever patch i've been playing (Opposing Fronts - Tales Of Valor), Pioneers just get slaughtered by Infantry Sections, even without a Lefty nearby. Spamming Pioneers is like the worst thing you could do...
Why not build HMG emplacements ? I would think that would help secure territory. Coupled with brens or recon tommies of course. This replay had not 1 building until near the end when he desperatley tried(Truck does not count)
Vickers Emplacements are good for defending choke points, and sometimes valuable Points, but they're really too expensive to be placed multiple times, just like every other British thing ever (aside from Trucks). Or maybe their upkeep is just too low, i dunno...