No: uPlan (and plan files in general) does not know, what a document is; the purpose of uPlan (and plan files in general) is to calculate the values of Content Objects - formerly: "ADORs"), that are in turn used to compose personalized message, whether in an InDesign document, an email, a Web page, etc.
The fact that both (the XMPie plan interpreter on one side, and InDesign on the other side) share the same programming language (JS) has nothing to do with it.