I know the guys up in Tianjin as well. There are a total of 5 foreigners at tianjin. 3 of them have been there a year and the other 2 just started a few months ago. They are all with WASINC (
www.wasinc.aero). I know WASINC is sending a quite few more this month as my friend is in the interview group.
I think VOR holdings (
Pilot Jobs in China - VOR Holdings - For a Safe Landing in China) also has a contract with them but like you said, they don't have a good reputation and I know for a fact that they don't have anyone working at Tianjin.
The contract is the same no matter which company you go with. I work at Shenzhen Airlines with WASINC and very happy with the support I get.