So this article says that the first group of 300 Whitefish contractors arrived in PR on Sept. 26th and they expected to scale up to 1000.

Can’t find anything on how many are there now total though, but it has been a month so I assume somewhere between 300-1000.

The first group of Whitefish Energy employees started work on the island upon their arrival Sept. 26. As of Thursday, Whitefish Energy had 300 employees and subcontractors temporarily relocated in Puerto Rico. The company expects to have a total of 1,000 people to be working on restoring power.

spokesman.com