Answer
Based on how it's understood to work, no — when a Business Reporter report's logic is converted into SQL and run server-side, the resulting data set is transmitted to the client as XML purely for rendering in Excel, not persisted into a queryable archive table the way Report Designer's %_REP output is. There isn't a documented, supported way to retrieve that XML data back out for reuse afterward; if you need report data in a specific structured format like a tax-compliant XML, building that from the same underlying data via Report Designer/an IAL (rather than trying to intercept Business Reporter's own transient XML) is the more reliable route.