http://europa.eu.int/comm/transport/..._poster_en.pdf
According to this, WHENEVER the flight is cancelled, you are entitled to hotel accomodation.
http://europa.eu.int/comm/transport/...ctsheet_en.pdf
If the cancellation, WHATEVER THE CAUSE, delays passengers five hours or more they are entitled to: Refund, flight back to original point of departure, meals and refreshments, and HOTEL ACCOMODATION if an overnight stay is required