Interesting, I'm sure that there are many secret functions on the mobile phone network but you probably have to get access to their computers.
I do know that the computerised mobile phone network has lots of functions to deliberately not let you create a PBX type of application because if you think about it, nearly every office in the world has a phone system, big bucks!
So cloned SIMS are out because just having a few mobile phones that all ring at the same time would allow you to have a simple phone system.
Cleared transfer of calls:
Hold please, put person on hold, dial new number, hang up to complete transfer or wait to announce call and then either hang up to complete transfer or un-hold caller to get them back.
Is jealously defended against for the same reason as above.
Where the fact is that we all, already have handsets and we could get along fine with just using them instead of also having a desk phone at the office.
