Still there and someone, the owner? has wiped off the ROWTOW marking that Sanitation put on it. Will they still tow it or does Sanitation have to mark it up again?

I remember being told by my tow guy that cars without plates or registration can be towed without a ticket.
So here is what I suggest: call a private tow company and find out if the derelict vehicle needs an NYPD ticket for a private tow? If not tell them where the car is (emphasis on a city street) and as a courtesy that the owner may live nearby (to avoid conflict).
If you do need a ticket file, a complaint with 311 again, it should be about three hours for the ticket to be issued by the NYPD and then call for the private tow.

Right now you are waiting for NYPD rotation towing and I don't think the car need to be marked by DSNY because rotation tow can take the car anyway if it doesn't have plates. If a private tow does the job the owner will have to pay the tow and storage fees. You won't be on the hook for that.

FYI - This vehicle is scheduled to be towed away by NYPD. We are awaiting an update on the date of removal but have been informed the process can take several weeks after the vehicle is initially marked for Ro-Tow by NYPD. We will post any additional information received here. Please post when the vehicle has been removed. Thank you.

Vehicle was removed over the weekend on 4-16! Thank you for the follow up.