I was reading an old Game Boy magazine ('tis about a year old) which had a feature on last year's E3. They had a full list of games that were on show (GBA only mind) coupled with a rough release date for each one. The first game under December 2002 was ‘Ghostbusters - Infogrames’.
I remember somebody posting a link a while back to some company's adverts or something, and one of them was the Ghostbusters logo with Infogrames' logo clearly visible.
Seeing as work on the comic-book revival had obviously already been underway before Red Ketchup announced ‘its coming’ back in January, maybe there's a connection?
On that website was just the logo, no screenshots or anything, so maybe, just maybe, this is part of the revival and they simply had to wait for the character designs to be finalised?