Typicially a SIM when entered in a SIM changes the default WAP
homepage to the operator that issued the SIM. How is this
accomplished? Is it via SIM toolkit and if so what *precise* commands/
method is used?

It depends on your phone, some devices can keep settings, some can
not. Some reset when a "new" sim is entered. You would change the
homepage via software in the phone or via a web page that the provider
list for your. It varies greatly from device to device. Clarify more
if this is not what you need.

I think I have made it clear I do not think you know enough about the
space to be honest from your question I am afraid.