HubPages states, "Through this program, you can refer new writers to HubPages and if they become Hubbers within 30 days, you receive 10% of their Hubs’ lifetime impressions."
So yes, if the reader comes to HubPages through your referral tracker you will get the sign-up credit. This includes sharing someone else's Hub. For example, if you tweet my Hub and you include your referral tracker and someone proceeds to sign up, you will get the referral credit.
The full Hub on this topic can be located in the Learning Center and is titled, Referral Trackers & The HubPages Referral Program https://hubpageshelp.com/money/Learning-Center-ref...
MissOlive / Marisa