Page 111 of my 2008 owner's manual states, "To improve the vehicle's traction when driving with snow chains, or STARTING OFF in deep snow, sand or gravel, SWITCH OFF the ESP system by pressing the upper half of the ESP SWITCH".

I think the idea here is ....if a tire starts to slip when starting off in snow.....the ESP applies that brake....& sometimes this just makes things worse. After you get going.....turn it back on.

I have an automatic now, but used to also have a 6 speed XF.....Tire Rack a few years back dumped a Blizzak "WINTER TIRE" that had gone for $400 when they first came out.....for $100.......You would not believe how it transformed the XF in the snow!!!!!!!!!!!