If I save a game and then launch a marketing campaign, then I go back to the main menu and load that save again, the marketing campaign is still active and the brand awareness rating is carried on. I get a marketing campaign for free.
I do this because I’m still trying to figure out how marketing exactly works. Once campaigns are finished, brand awareness will fade slowly. I usually wait for it to go down a bit before launching a new campaign, but often I get no increase in brand awareness from it (possibly because the campaign didn’t yield enough brand awareness compared to what’s left from the previous one). It’s a bit obscure, and trying to figure this out I went into that bug.