Would really like to see some discussion on this. We just experienced some severe cold weather in Atlanta, GA and several questions were asked on if aerials can/should be raised on ice/snow. After serving several years on departments in Michigan, Massachuesetts & Virginia I have a little knowledge on this.
I don't think that there should be any question on if an aerial can be raised on ice/snow. The answer is yes, in most cases, with steep slopes or grades being the possible exception. If you are on a solid surface, such as asphalt or concrete, go with bare feet (no ground pads), other situations are judgemental based on conditions. Either sand or salt works, each in it's own way. Salt can melt the ice but will refreeze when washed or melted away. Sand provides some additional friction for the pads but given the weight on the pads and that the majority of the force (gravity) acting on the pads is down, it is really negligible. I have found that a combination of the two works the best, with a 2or3:1 mix of sand to salt. The weight of the apparatus should give all the traction you need, but the operator needs to be constantly monitoring any movement, as always, and adjust use & tactics accordingly.
Needless to say, being in the (normally) sunny south, our department doesn't address this in our policies or guidelines.
We use rock salt under our outrigger pads as well but I have worked at a dept. a few years back that used sand. Both worked well. We are also testing an ice cleat this year as well we have tried some in the past didn't work out. Been a lot of positive feedback so far. It's the Spiky and Spiky Plus model. They have industrial special pricing if you buying for the whole department just need to contact them. Heres their link www.spiky.com