If a business has multiple copper lines, is there any way to get a call going out on any line to report just the first line in Caller ID?

It depends upon the local service provider. Some will send data for any number in the group as the main, but ILECs like Verizon don't like to do it. I'm not even sure if they will do it. If the service provider is a CLEC, you stand a much better chance of getting them to do this for you.

Is there any way for the PBX to control what number will appear in CallerID for outgoing calls? Or what kind of outside line do you need to get this? Will an ISDN BRI line do this? I guess an analog line won't do this, or can it?

You will need a PRI circuit to manipulate the outbound CID information sent with a system capable of interfacing with it. BRI circuits are going to be very difficult to get for a new installation. There is no way to manipulate outgoing CID data on any kind of analog line unless the telco does this for you.