You would need to trap the RAW events returning lusers info:
raw *:*:{
if ($istok(250 251 252 253 254 255 265 266,$numeric,32)) { echo -a 0,4 $iif($istok(265 266,$numeric,32) , $4- , $2- ) | return }
echo 5 -a should not see this: raw $numeric : (1) $1 (2) $2 (3) $3 (4) $4 (5) $5 (6-) $6-
}
The 2nd line should be ;commented or removed once you have it working correctly, because otherwise it echoes other things at other times too. It's possible your server can return additional $numeric info that I'm not seeing, so you would then need to add those to the list of handled numerics.
The ON TEXT event only sees when someone else chats in a channel or query window.
Also, reminder that -a is the active window which might not be a #channel.