I assume it was private, much of this is pretty close to the people working with it. Besides, I doubt they would make a public screening of the new footage before showing it to the producers anyway. At the very least, any public screening would have had to be through some approval measure anyway, so that'll take time.
The same news story made it to The Futurama Point (http://slurmed.com/news/2010-03-12/futurama-season-6-video-format-special-guests-and-progress
), which contained a bit more detailed information regarding who said what.
Our sources for this kind of information remains people inside
the production team who posts this information around the Internet.
Long story short; it was a screening to the producers, but it marks a milestone in the production of the new season, because it means that the animation team is working quickly. And most definitely will make it by June.