using AssemblySearchPaths in csproj files

Can you change the value of the "AssemblySearchPaths" property within the Target "BeforeResolveReferences" and see if that solves your issue?

    <Target Name="BeforeResolveReferences">
<CreateProperty
    Value="..\Dependencies\VS2012TestAssemblies;$(AssemblySearchPaths)">
    <Output TaskParameter="Value"
        PropertyName="AssemblySearchPaths" />
</CreateProperty>
</Target>