I've done it multiple times, while pretending to be jettarding, just so I could attack the enemy base. It works surprisingly well. Well enough that my Painsaw bind buys Jetpack, Grenade as well as Painsaw. This is mostly for maps other than ATCS, though, such as Niveus, Nexus6 and Karith, in which there are numerous scenarios for which a jetpack can come in handy.