I have implemented my custom project subtype and trying to persist the configuration specific data using IVsBuildPropertyStorage as described in Persisting Data in the MSBuild Project File but all properties that use MSBuild style values $(ProjectDir) are escaped as %24%28ProjectDir%29 and this result in properties being not usable from MSBuild.
I see this problem has been described before in this thread but so far I haven't found any solution, isn't posible to get the values saved without escaping values?