Hmm..ok, I tried it, using the 'link existing accounts' thingee here on HP, and after filling out all the fields and clicked "Link My Accounts" .. absolutely NOTHING happened!
No confirmation page, nothing. Earlier, I was having problems with it telling me I had an error in matching the phone number, so I went and checked it from my original sign-up site, and no, there was no error made, so there was an error in the processing software someplace.
Since nothing has 'confirmed' yet, I still don't know whether or not it worked. It's been a frustrating day.