ive been watching HLSW, in the mornings when every other servers is empty except 1.6 (which has about 12~ people at 9am), pings are fine, no lag or spikes
At night when the servers get full, they lag. Not just for 1.6, but for all the servers.
So basically it comes down to CPU not being able to handle the load, I think Nickname said GG:S was at 100 ticrate? I would imagine that has something to do with it.