"drush up" fails with "pm-updatestatus failed."
I was able to fix the problem by editing the file /path/to/drush/includes/exec.inc and changing line 331 from

return _drush_escapeshellarg_windows($arg, $raw);


to

return _drush_escapeshellarg_windows($arg, TRUE);


as described by peterromero here https://github.com/drush-ops/drush/issues/2152