Depends on what access basis. If just by flying business class, then you are restricted to your terminal. Otherwise yes, if you are allowed to cross imigration (sometimes they require booking cards too to allow you to go to a specific terminal). So it very much depends what you want to access and what are your credentials. Easiest on departures out of Schengen through CDG is to first visit the Schengen and then non-Schengen lounge.