Edit: confirmed to also work with aspect of the fox (see: video in the comments just below), so any class can use this with the help of a hunter.
Hey. While I'm sure many mages have experimented with Icy Floes, I'll start with a basic explanation: It's a spell in the first tier of mage talents (level 15) that allows you to cast while moving. Originally, I figured this would only work with mage spells, like Presence of Mind and such. However, it worked on mounts, and as I've now found out, much more - you can use it to capture most channeled things, including (but not limited to) objectives in battlegrounds.
So, a quick how-to, and then for some more advanced stuff
1) use icy floes
2) right-click the PvP object you want to start capturing (for the sake of simplicity, say a flag in arathi basin)
3) move around freely while capturing the flag
4) return to the flag before the capture ends (important - otherwise it will just tell you you're out of range and the capture will fail).
5) ???
6) profit (capture complete)
So far I've tested the following mechanics (in addition to regular movement) that have not interrupted the capture:
Displacement: Typhoon (Druid), Leap of Faith -- allowed me to ninjacap EOTS mid flag while standing below the platform, just had a friend Leap of Faith me up at ~2sec remaining so I could run back to the flag
Stuff I've tested that I know don't interrupt casts during icy floes, not sure how of applications:
Goblin Glider (allows for in-air portals, although I guess the negative side is quite obvious: you have to cast the glider before you start casting anything else)
Stuff that I've tested so far that DO NOT work
Alter Time. Unfortunately, it won't pull you back while a cast is in progress, rendering it useless as far as BG captures go - although you do get to keep mounts and such you've cast during Alter Time once the it pulls you back, so you can always make great escapes using the mechanics to your advantage.
Use at your own risk - blizzard does not like pvp exploits generally speaking, although I suspect using your class spells is one of the less noticable/punishable ones to try.