Assume that 1.rpt file has three parameters named Country (multi value), BalanceLowBound (discrete value), CreatedDate (range value), the add-on can call the following method to get the xml string exported:
SBO_Application.ExportRptAsXml("1.rpt", "Country=0:DE,US;BalanceLowBound=1:1000;CreatedDate=2:2010-01-01,2010-12-31");