This check will fail at least for Linux 32bit builds when you have an entry for Linux64. So it also evaluates to true:

´linux´ in ´http:\/\/ftp.mozilla.org\/pub\/mozilla.org\/firefox\/tinderbox-builds\/mozilla-central-linux64\/1376463937\/mozilla-central_ubuntu64_hw_test-tp5o-bm51-tests1-linux-build199.txt.gz´

We might still get the same timestamp, but just for safety reason we should correctly select the appropriate entry.

So I would suggest we extract the branch, platform, and debug field for ´\/mozilla-central-linux64-debug\/´ and do necessary checks.