CREATE TABLE #t (id int, t timestamp)
INSERT #t (id)
VALUES (1)
DECLARE @d xml = (SELECT t AS tmstmp FROM #t FOR XML PATH(''), ROOT('row') )

SELECT r.p.value('tmstmp[1]', 'timestamp') from @d.nodes('/row') r(p) 

DECLARE @docHandle int
EXEC sp_xml_preparedocument @docHandle output, @d

select  tmstmp 
from openxml(@docHandle, '/row', 2)
with (
	tmstmp timestamp
	) 
exec sp_xml_removedocument @docHandle
DROP TABLE #t