No success whatsoever in either direction across Samba. In fact the mtime of my Linux home directory as seen from NT is Jan 1, 1980.
That's only the case for an NT mount point (something of the form \host\name; I notice that os.stat() only believes it exists if you append a backslash: \host\name). For interior directories, at least with the Samba version that I'm using, os.stat() seems to give correct results.
I think that this whole issue (that doing a stat on a directory to find out whether files in it were modified doesn't give usable results) is widely blown out of proportion.
The only useful bit of info is that mtimes may have an up to 2 second granularity, and that anything as recent as 2 seconds should be considered as newer than the cache even if the cache is also less than 2 seconds.
--Guido van Rossum (home page: http://www.python.org/%7Eguido/)