If the demand is great enough, they can fly trades to site and put them up in a hotel, just like any consultant.

That is done, but it is more expensive so it isn't common. In most cases the trade is needed and busy in their local city so why would they leave to a different place. Trades that have niche skills fly all over, but electricians are something that you need all over and so most can stay busy working close enough to their house to see their kids every night.