Google recognizes each hubpages account as subdomains...yes!
Each account is separate that is why, in the hubs stats you can tell from which other domain visits came from, for example you may see some traffic from another hubbers account. Someone might have clicked on a link from the related hubs section so it records that visit as unique.
All traffic is now recorded as separate, HP traffic is from hopping and clicking on hubs form the hubs category, all other traffic names the sources such as the hubbers domain.
I hope I explained it well.
The simple answer would have been yes. Active participation does help, it's like getting traffic from other websites.