I was flying that day and yes we hold over KEF waiting for an improvement but we knew that conditions were not good long before. RWY 02 has an up slope gradient so you don't even have to use brakes or rev to stop the 757 at std spd (125-145 kts).
Maybe they were too fast at the end of the rwy? By our experience in winter ops we know that icy patches or low braking action + snow = trouble in KEF. JetX crew had a loooooong duty that day. The nose gear is also at an angle of 90°. That will not do the turn on a slippery taxyway. You first have to try to reduce the angle to regain control, but all this is only speculation as we are still waiting for the report.