Is there a way to export settings for C# formatting at a project level so that we can put the settings file on a repository and everyone can use it without affecting other projects that are using different formatting styles?
For Visual Studio C# environment settings, you can Export them from Tools->Import and Export Settings->Export Selected Environment Settings, then save the file.
You can store this file somewhere on the network, in Source Safe or TFS.
Then the other devs who want to use those settings will Import them Tools->Import and Export Settings->Import Select Environment Settings, select the file and press import.
It can also be loaded from command line, or a desktop shortcut
Devenv.exe "C:\MySolution.sln" /ResetSettings "C:\MySettings.vssettings"
Consider the Code Analysis Policy Editor in Check-In Policies.
If what you are looking for is not built in, you might need to look for an Add-in, CodePlex has over 500 of them. If you don't find it, you might have to make Make one.
Another possible solution is to bring the teams together in a coding standard meeting where they can agree on a common coding standard, then use a tool like CodeIt.Right to do the code refactoring automatically.