Steelpaper, In cases of criminal behaviour my experience is that you have to look at whose self interest is served by the missing extinguishers. In my view in your case it has to be either one of two bodies, either the company who subsequently tendered for the replacements or the EC by a ‘cosy’ (think Labor Party power brokers and headkickers*) arrangement.
[*Cosmo named names here but, since he hasn’t deposited $1m in the Flat Chat Defamation Defence Fund, I have edited it out]