This thread will probably be moved by a moderator because it doen't really involve help with scripting.
Nonetheless, I may be able to give you some guidance because I have frequently been asked in the past to set up a channel relay botnet, most particularly when world cricket competitions are in play (there is a cricket based IRC network).
A word of warning though. It isn't easy. Even with experience it takes me a while to set it all up.
You need a botnet (linked bots) and a channel relay script. The method I use requires 1 bot per network/channel.
The botnet need only be of a simple type. You do not need synchronisation of information, hence the share and transfer modules are not required neither are the associated bot flags. Just hub/leafs created in the normal way by adding each bot to the others (with valid hosts and telnet ports).
The channel relay script I generally use can be downloaded from the following URL :-
http://nemesis2.qx.net/pages/Eggdrop_Scripts
The script must be loaded on each Eggdrop bot and individually configured depending on what you want each bot to do. The script allows transmission of IRC events to other networks/channels, receipt of IRC events from other networks/channels or duplex (both simultaneously). The script can be configured to exclude or include the wide variety of IRC events that normally occur such as joins, parts, channel messages etc etc.
Good luck with it. You'll need lots of patience.