If its like the others, cgminer, bfgminer, then you just add more servers, username and password sets to the command line.
like,
minerd -server1 -username1 -password1 -server2 -username2 -password2 -server3 -username3 -password3
but using the correct details.
Worth a try?
It doesn't work...
I've tried:
minerd.exe -a quark --url
pool1:0000 -u
user -p
pass --url
pool2:0000 -u
User -p
Pass -t 3
And only connects to the second one...