The problem is in your test projects. you're referencing to some assemblies which haven't been deployed to the Build Server(TeamCity). Also you cannot do that by simply copy and paste to GAC or working directory.
The best and easiest way to do that is installing Visual studio 2010 Agents in the build server. It's free and it can be downloaded from MS web site. By installing the agents, it will install all the required libraries for compiling and even running the MSTest projects.