Okay, if I understand you correctly, the problem here is that when the link is visited, the Google tracking code never actually gets activated, right?
I see two potential fixes.
One is to make the XML document into an XHTML page so that the Google tracking code can run on it.
The other is to setup a custom WordPress page … let’s pretend it’s page ID is 1365 and name it podlove1365.
The custom page does just two things. It runs the Google tracking code, and it delivers the mp3 file.
The URL would be something like this:
All feed urls would run through this custom page.
Neither solution relies on directly interacting with the Google API.