Erm manual:

OW:T
Set/check/get Alliance Team
    $1 - Color (See Format E1).
    $2 - Team (0..6)
Set/check/get $2 Team for $1 Color (changes alliances).
Please note that if owner is neutral (value for object owner is -1), there is no need to get alliance team.
   If however you do so, the resulted team number is shown as 0 (which in most cases is the same alliance number for human red player).
   To check if owner of i.e. a castle is neutral use see CA:O command

To add:
The alliances you set during the game will reset on each reload.
So any change with OW:T must be present also in GM0

I edited my erm help but not sure what tool to use as when saving in word, it comes as different html file.