Much as i looked forward to a snowy SA, last year it was fun being able to really exploit the 4WD's and a rally-spec Warrener and let's not forget the intense fun of driving a completely overkill muscle car in snow, i'm actually glad it lasted maybe one whole day online.
Call it coincidence, call it bad luck if you will, but it's highly unlikely to be caused by contention/congestion - but when the virtual snow was down, you couldn't get a stable session on NG here without it randomly bombing out with the usual first 'your network was lost', followed by the obligatory "Rockstar Services unavailable", which required a full game restart from cold to fix.. for a short lived random period (and no, it wasn't anything my end either - there was zero network or device issues here, on 4G or the big bandwidth broadband). Giving it up as getting too damn stressful for Christmas Day, fired up the PS3 and wow, no bloody random drop outs with snow down.
24 hrs later, no snow, and all is well on both fronts. So, maybe there was NG side contention/congestion but it seems weird that it went away with the snow gone. Dunno if it happened on the PC side or not, didn't attempt to investigate there.