Awk
solução:
awk '/<\?xml/{ date=$1 OFS $2 OFS $3 }/rc_transaction result=/{ print date, $2, $7 }' xml.log
A saída:
03 Apr 12:48:42.503 result="ok" sequence_number="117749"
03 Apr 12:49:21.936 result="ok" sequence_number="117750"
03 Apr 12:49:39.654 result="ok" sequence_number="117751"