Register extensions with the same name on different servers

HI, recently i have received a request from various persons of the enterprise where i am working, to create various user extensions, that have the permission to listen and whisper on fop2 , the company has four differents sites on 4 different cities, everyone of these has its own server and its own free pbx installed with different pool of extensions, to be able of Listen and whisper in fop2 it is necessary to have the extension you are using registered in a phone, so you can hear what is being said on the call yu want to spy, the people asigned for these users are located in the main site , in just one city , they arleady have an extension but their extensions are only registered in one server not in the other ones, can i register the extensions they have on the main free pbx , on the three other free pbx servers ? with iut any problem , and that can use the whisper and listen function on fop2?

So essentially you want to use fop2 to spy on extensions that are on different servers?

You have to manually setup the users and buttons that are sitting on the other servers.
Here are a few threads discussing that.

Easiest way would probably be to pay the fop2 developer to set things up for you, might be two to three hundred bugs.

thanks a lot dude , but on older versions of fop2 that could work? i mean some older versions run different