Hi,
To have incoming calls directed to Call center agents isn’t any problem since that is what call centers actually do.
As to forwarding the calls to another party that is not registered to the same pbx it is not much of a problem either you just need to think a bit about how you are going to make that more cost effective.
The agent is first going to call the employee located elsewhere and then if availiable will transfer the call if I understood correctly. That involves connecting your pbx with the pbx of the employee , what kind of lines are you going to use for that? What kind of facilities do you want to provide over that media and how many simultaneous calls?
Are you going to just send sms or call your clients anywhere within the country -in which case an sms server and some gms gateways will be enough- or are you interesting on providing them with internal phones factionalities (like being able to set up a call back)? If you want to have the second then you need to have remote extension factionality.
To be honest can’t give you much of help here since there are a lot of clarifications needed but still hope I help you a bit.