helps to have it.  It's better to have it and not need it, than to need it and not have it.  Everytime that we go out to the sawmill, we bring the company welding truck.  Not only is it great to have when a welder isn't available in the area of the mill we're working in, but it has cabinets for pretty much everything we'll need while working away from the shop!

That said, in the end it depends on the contracting company and where the work is located.