I may be no expert in scripts, and I didn't make it (obviously) but I think scripts mostly run on all accounts logged into plus! live.
There is some scripts that can make it work for only 1 address, I saw it in the scrip making for newbies guide and you can change the automatic activation (the part that switches it on when you open messenger) to only activate when you sign in to a certain e-mail address, then you could PROBABLY copy the entire script to run a whole seperate set of answers into a new script.
This would mean having 2 of the same script logged into different e-mail addresses, so your script list should show something like this for the sake of less confusion:
{other script(s)}
Answering Machine Plus for (certain address)
Answering Machine Plus for (certain other address)
{other script(s)}
Basically change the very beginning bit to activate when a given e-mail address signs in on your computer and copy it into a new script file for the other, then you can make 2 sets of answers for each address.
If I find out what the exact command is I'll write it up for you and post it here for you to replace the original.
EDIT:
THIS should hopefully (when changed for your e-mil address) work your answering machine ONLY on the sign in of the given address.
If you want a seperate list of answers for a second address duplicate the entire script into a new script file and change the e-mail address your second script works on.
This only MIGHT work.. If not I'll just have to keep looking, let me know OK?
code:
function OnEvent_Signin(Email) {
IsOn = GetBoolOption("IsOn");
}