No, and maybe.
Every Pier Comes with Backup Power
The power cord at the base of your pier is backed up with an uninterruptible power supply that will run your rig for an hour or two. The exact duration depends on how much power everyone else is demanding. Since most power outages are very brief, you may not ever see the power go out.
But...
For a longer outage, that backup might run out. If you would like to react to a power outage in some way — say by stopping your sequence and homing your mount — you won't have an opportunity to do that unless you have your own UPS that kicks in when ours runs out. If you have a plugin that watches for such things, or if you want to set up a script on your PC that runs when the UPS is engaged, your desired action can happen when the power goes out.
But...
Power outages are most often storm-related, and during storms, the roof is closed and you won't be imaging. So there may not be anything you need to do when the power goes out.
So...
Most people don't need a UPS. If you'd like to have one, keep it small enough to sit at the base of your pier and not get in the way.
For What it's Worth...
The roof is on its own UPS. If that were to fail, the roof can be closed manually.