Currently you have to explicitly request them via '-l release=trusty'. This will need a *lot* more warning and work than converting the webservices, I think.
== Announcements ==
* https://lists.wikimedia.org/pipermail/labs-announce/2016-August/000144.html
== Details ==
* https://wikitech.wikimedia.org/wiki/Tools_Precise_deprecation
== Timeline ==
* late August 2016: Jobs started without `-l release=...` and webservices started with `--release=precise` will print a warning.
* mid October 2016: Jobs started with `jsub` will no longer run on Precise hosts by default, and will instead run on Trusty hosts. This means jobs running via cron will migrate to trusty automatically.
* October 2016-January 2017: Tools starting jobs with `jsub -l release=precise` will start receiving emails urging them to migrate to Trusty.
* March 2017: Jobs started with `jsub -l release=precise` will no longer function and will crash with an error.