I just purchased one on ebay. It isn't a free trial. You keep your old account, and I have already used my free trial. Under my account settings it now says:
You are currently using Spotify Premium. Your account is associated with our partner Telia, please refer to Telia for questions regarding your subscription.
It seems like Telia (Euro phone company apparently) has some kind of plan that includes Spotify. I didn't really look too far into it.
Seems legit, but we'll see what happens in a month or two. Even if I just get 2 months out of it, I come out ahead.