I booked into Hilton Club NYC via RCI.
So yes you can do it.
Problem is this, HGVC deposits units into RCI prior to 9 months out, but as a previoius poster mentioned they restrict HGVC members from booking 9 months out to match the internal club season restrctions. It is possible that many or all of the units have already been picked over before the 9 month windows is open.
They also deposit mainly Orlando , Vegas and Big Island HI, occassionally a very limited number of Oahu HI and some NYC, and CA (via the new deal with the GP).
It is possible to get the unit cheaper points but remember you have to pay the RCI exchange fee which is nearly 4 times the price of the internal HGVC fee of $49.