Since this thread got bumped... I noticed today that Recovery Sappers have a reinforce cost of 28 whereas vanilla Sappers are 26. Not sure if it's a bug per se' or just a weird balance oversight since I can see no reason for the cost differential.
Intended I believe.
Correct me if Im wrong but I think they are just a better version of normal sappers as they can scavenge wrecks, get a sweeper for free and throw smoke grenades.