I think the author you quote has got some of his information mixed up.
Coventry was bombed in Nov 1940, and this was known from the Ultra decrypts about 48 hours before the attack took place.
It is true that the decision was taken not to take any special precautions to avoid alerting the Germans to the success BP were having in decyphering their radio traffic.
BP had no captured enigma machines at that time, the decrypts were done using a machine devised by Alan Turing.
I think the first machine was captured from U110 on 9th May 1941 by the Royal Navy.
It is surely stretching the imagination to assume any connection between Coventry in Nov 1940 and Dresden in Feb 1945.
WC
