I figured the version of Honeycomb that shipped with my Tab was burned onto a ROM or something, because the last time did a reset, it wiped out things like the update to Google Play from "Market".)
So, it was a surprise to me that the ICS update completely overwrote the original Honeycomb stored in the Tab.
Normally, when I upgrade or install a new OS, I'll wipe the drive and do clean install. (at least on a PC with Windows)
But in this case with a mobile device, I could only see upgrading as the carrier specified. I didn't find any other way to upgrade to ICS...unless rooting it and downloading it from somewhere would do it.)
Anyways, it's all good now.
I wrote the original post so that it'll hopefully get Googled...and then other Telus Tab users might find it when searching for why their Tab suddenly has the battery life of a radio shack alkaline after the in-place upgrade.