Why would Mike give the German engineers his real name? When the head German engineer and Mike are talking in S4E7, the engineer tells him the meaning of 'Ehrmantraut' - This seems sloppy after all the trouble they go through to hide the location of the facility. Are they planning to kill them all anyways?
I have a few possible theories:
1) Mike trusts the head guy. I don't know that any of the other workers overheard Mike's real full name being used, but I could be wrong.
2) Finding someone only by their name, even an uncommon name, is no easy thing. It's not like he shared his social security number, and I doubt in this world you'd be able to type Mike Ehrmantraut into google and find a hit that's our Mike. If you did, it might be his listed employer, and good luck finding him that way.
3) Mike has Gus to back him up. I'm sure the guys hired here are aware of the monumental amount of wealth and therefore power that Mike's boss must have.
4) Mike's a former cop, I dont think much scares him. Especially if he can stand up to Fring.