import re
 
 
lst = ['MEASUREMENT   K02313  New York',
       'MEASUREMENT   K02338  London [BC:2.7.7.7]',
       'MEASUREMENT   K14761  Kairo [BC:1.2.-.-]',
       'MEASUREMENT   K03629  Berlin',
       'MEASUREMENT   K02470  Paris [BC:5.6.2.-]',
       'MEASUREMENT   K02469  Madrid [BC:5.43.2.2]'
       ]
pattern = r"\bBC:(?:[0-9-]|[1-9][0-9]|[1-9][0-9][0-9])(?:\.(?:[0-9-]|[1-9][0-9]|[1-9][0-9][0-9])){3}"
 
print ([m.group() for s in lst for m in [re.search(pattern, s)] if m])

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