[Someone]

Define 'similar'. Do both firms have to go through the same amount of red tape? If not, is time spent doing extra calculations showing the safety of the bridge productive time or bureacratic overhead?

You _can_ let both design a bridge according to the same rule set, but to measure how hard teams work and not how fast they can do that task, you have to make sure both have equal experience with that rule set (US engineers will likely be faster at designing a U.S. bridge than UK engineers, and vice versa)

To make a truly fair comparison of efficiency of working, you probably will end up with an exercise where both teams design a bridge that will never get built. Possible? Yes, but also expensive.