I recently purchased an HP Deskjet wifi-enabled printer (model no. 3515). Set it up successfully as good as that both me (in the same network as the printer) as well as another person few miles apart from me (having different isp than mine) could print wirelessly successfully.
The printing across network (printing from a network other than that to which the printer is connected) has been set-up and tested successfully both through Google Cloud Print and HP ePrint Software.
However, when it comes to scanning across network, or cloud scan as we may call it, none of these two support, or even say anything about, it. Talking to an HP customer care executive about it was fruitless as i expectedly got no better answer than 'it is not possible'. Also, unfortunately, I have not found anything worthwhile on internet regarding this either.
What my understand is - if printing could be done wirelessly across network, so could be scanning. After all, in both we do roughly the same thing but in opposite direction. That is, in layman's terms, if i am not wrong, in printing we convert digital information into hardcopy document, and in scanning it is just the other way round.
Please correct me if am assuming too many things too wrong.