You could deliver a radar picture on a 38400 baud RS232 link! It's vector data, not raster.
It's true that a 2mbit/sec leased line costs a few k but
a) you don't need that speed
b) the "leased line" actually runs on the BT ATM network anyway (unless you got a point to point microwave link for some special reason) so there is no special reliability or redundancy.
You can still rent a traditional leased line from BT. I don't know what they cost but everybody knows that BT resisted providing ADSL for years, because this was going to cut into the big revenue they were getting from 64kbit/sec leased lines. Those lines were physical wires, I believe; certainly in the old days.
Anyway, these are details; the problem is in the organisation and the regs governing who is allowed to use the data.