Singapore Airlines has an all-business class flight from EWR-SIN (Newark->Singapore), but I can't seem to find any reward Krisflyer flights for any dates.
SQ often blocks partner awards for very exclusive classes/flights - like their Suites and the EWR-SIN flight. So it will make a difference if you are trying to use SQ miles, or miles from another *A airline.
This blog post has some information in the middle that might help you: http://boardingarea.com/blogs/onemileatatime/2008/05/03/award-booking-question/
It seems to suggest that only one seat is released per flight.
e: update -
Only Standard and Full awards are available for redemption of flights on the all-Business Class A340-500.
This would imply that they do release seats. I would expect, however, that demand would be pretty high.