Bridge Engineer Question

[Engelbrekt]

The rules say:

...an engineer company will have a probability of bridge completion 1/3 that of an engineer batallion. Otherwise, having more than one Engineer unit constructing a bridge will increase the chances of completion.

But what about two bridge engineer companies combining? They are not a full batallion, what are their chances? Is is worth combining them?

This is regarding the MG44 Alt campaign, the new rules (quoted above) and the Allied 30% chance of bridge building have the effect that bridges are somewhat difficult to build... The two companies have been trying for 14 turns building a bridge for the 30th Corps armored elements to use..

Anyone have any answers to this? Would be appreciated.