Alex
I do not know the details of the protocol, if it is simple character based then you should be able to do something with the revision 4 hardware controlled from the gateway.
If you go to http://docs.webbrick.co.uk/WebBrick/CommandSheet6_50.pdf you will get a later command reference, this includes the supported serial commands for version 6.4 (it is the upcoming 6.5 manual).
You send the command
CR4 to put the port into 485 mode (9600 baud only on 6.4 firmware)
RO to out the RS485 into output mode, remeber RS485 is half duplex.
RI to switch to input mode.
RD to send 1 or more bytes of data.
Inbound serial data is delivered to the network as a UDP event and can be picked up at the gateway.
In the long term we expect to embed some serial protocol support within the webbrick, but it will be for very common protocols only, otherwise we would implement in the gateway and use the webbrick as a remote serial port.
Lawrence.