There are numerous ways of writing this:
"Owing to a signal failure at Three Bridges, services are severely delayed." could be followed by any of:
1 We are sorry.
2 We are sorry for the inconvenience.
3 We are sorry for the inconvenience caused.
4 We are sorry for the inconvenience this has caused.
5 We are sorry for the inconvenience caused by this.
1 and 2 are too abrupt. 3 and 4 are typical, 5 is too wordy.
So, Niwantha, yes: form 3 is the result of contracting the sentence, removing an unnecessary reference to 'this' which is obvious from the context. Your example (lack of preparation) doesn't quite work - the lack of preparation needs to have been mentioned already for the contraction to work.