I'd like to know whether I could have the web access statistics for
    the package I maintain. basically, I'd like the number of downloads
    of the package tarball vs time.

I don't think it's possible.  In general, downloads are redirected to a
random mirror and there is no mechanism to collect or collate the
results.  So any numbers from savannah itself would be useless.  As far
as I can see.

Best,
k