I've seen it bothways.
Keyplan referenced seperatly, which means each file is created they need to
bring in the xref. Not a big issue when it's your office doing all the
sheets, but can be when other trades are creating their own sheets. Giving
the other trades a KeyPlan drawing to xref in would be best.
The other way, where the keyplan is part of the template, involved a special
template created for that one job. A good idea when the job requires 100's
of sheets. And all the trades use your template for the job. The template
does need to gice a space for each trade to import there LOGO, etc...
Depends on the size of the job, and the amount of different firms creating
drawing for the job. And don't forget about coordination drawings, if it's
part of the contract. They to need a KeyPlan.