Comment 1 for bug 868329

A solution to this would be to add another function in file module for resolving a file path with a given absolute URI.
file:path-to-uri($baseUri, $filePath)

So file:path-to-uri("file:///C%3A/path/file1", "e:/path2/file2")
would produce "file:///E%3A/path2/file2"