IIRC, when we were evaluating GPRS modules for potential use in the hiptop, we would consistently find ourselves testing modules that worked well for a minute or two at a time but would fall over flat if you tried to keep a connection going for any length of time.
If all you needed was a few dozens of seconds of connectivity — such as, I'm guessing, to update a sign — that was probably just dandy. However, that's not how the hiptop worked; it generally aimed to open a connection to the "mothership" soon after boot, and it would hold it open, for hours or even days, network willing.
If I remember correctly we had it up and running around Q1 2000 which seems to be before this (Not quite sure though, the article doesn't mention specific dates)