Meanwhile I have solved the problem myself:

;WITH XMLNAMESPACES(DEFAULT 'http://www.k-5.at/Schema/Entleerung:001')

SELECT

e.z.query('data(./ÖStatNummer)').value('.', 'nchar(5)') as GemeindeKennZiffer

,substring(e.z.query('data(./Erstellungsdatum)').value('.','nchar(10)'),1,4) as Jahr

,substring(e.z.query('data(./Erstellungsdatum)').value('.','nchar(10)'),6,2) as Monat

,'D' as Recordtype

,k.y.query('data(./Tagnummer)').value('.','nchar(16)') as TAG

,k.y.query('data(./Kunde/EDVNummer)').value('.','nchar(16)') as Personennummer

,ku.v.value('.','nchar(20)') as Vorname

,k.y.query('data(./Kunde/Adresse)').value('.','nchar(20)') as Adresse

,s.o.query('data(./Objektnummer)').value('.','nchar(16)') as Objektnummer

FROM (SELECT XmlResult...