If you are using to register the module regfile, then you do not get to do it.
If you are using a module register, then you can only do this by implementing the appropriate logic to the database.
But, IMHO, is not necessary to assign different devices to the same number.
As a workaround, I can offer you the following simple solution.
Assign devices hidden numbers, for example 99991111 and 99991112 and in regfile.conf write:
[99991111]
password=pass1
alternatives=3001
[99991112]
password=pass2
alternatives=3001
And then, dial of 3001 you will ring both devices.