airControl - Does AC2 Safely Upgrade Devices with PoE Passthrough Enabled?

Yes. AC2 does topology-based ordering of devices while doing firmware update to make sure it doesn't start flashing any two devices that are 'tied up' together via PoE at the same time - doing so can cause power hiccup on the power giving device (e.g., TOUGHSwitch) and thus the power receiving device will fail to finish flashing process and fail permanently.

When you select set of devices to update FW, AC2 partitions them into batches, all devices within a batch updated in parallel, while batches themselves are scheduled one after another. Within a single batch there should absolutely no devices tied with PoE relations mentioned above and having correct topology ensures that.

If AC2 detects such batches it will have batch-number (written within the parenthesis) in the "No." column of the task's item list, which you can check if all PoE-related devices land in different batches