If you contact the mill, they maybe can perform the CVN there, rather than you having to go to all the hassel. The project I'm on now had that same spec requirement (also DOT). They originally wanted a CVN for "each A500 HSS tube (thats each piece for each brace) to be used in construction. It was finally agreed upon to have it done by/at the mill, in sections. You might give it a try?
If its just BM and not related to a PQR you may be able to get data from the manufacturer off the MTR. If its not on the one you have it may be cheaper to ask for it with Charpy's than to do your own test. If the test temp is equal to or lower than your required 40, as long as you hit the 15 ft/lbs you're good.