Bell and Telus' massive, sudden addition of nationwide HSPA networks to succeed their legacy CDMA towers was an experiment unlike anything the wireless world had ever seen; at no other time had carriers that large jumped from one 3G technology to another, and it was anyone's guess how well it'd go and what effect it'd have on their bottom line -- clean-slate network build-outs aren't cheap, after all. We've got part of that answer now that Bell has reported fourth quarter earnings, and in a nutshell, it seems like this may have been a huge gamble that paid off. The company's wireless unit saw a 2 percent decrease against the previous in EBIDTA -- and ARPU fell by CAD $1.48 to CAD $51.08 -- but here's where the bubbly gets broken out: it saw a 39.3 percent increase in gross activations to 523,000, up 11.3 percent year-over-year. That works out to 163,000 net adds, almost certainly attributable to the launch of HSPA service and a variety of hot new handsets (and some older ones -- the iPhone 3GS, for instance) that gave some disgruntled Rogers customer the ammo they needed to bolt. It'll likely be a good long while before Bell actually goes net positive on its massive network investment, but early signs certainly suggest that it was the right move to make.