Not automatically no, but you can use repeater to make it much easier at least. First make sure your account names are entered correctly in isboxer. When all isntances come up they will have the correct login names already.
If you do that, and all your accounts have the same password, you can toggle repeater mode on after all screens are up, click anywhere to get the login screen on all instances. The password field will already be focused, so just type in you rpassword and hit enter, then hit enter again on the server select to use the last played server. When all character selection screens load, hit enter one more time to load the last played toon on each.
Then remember to turn repeater mode off