This would be anything that violates an individual, or companies "reasonable expectation of privacy". Section 8 of the Canadian Rights and Freedoms. You folks have an amendment to your constitution on this (...4th?). Private residences would have the strictest expectation of privacy: anything not visible from public property could be reasonably expected to be private. Businesses open to the public or bare land have a moderate expectation of privacy. Business that are not open to the public or restricted areas in businesses that are open to the public would have a higher expectation of privacy as well, particularly in this situation with security involved.
If information has been lawfully obtained by a building inspector through an administrative process, but that information is otherwise private, it would be a violation of the law to release this information.
Is it just the security folks asking you to sign? They might have been told that everyone entering the property who are not staff must sign and are not aware that there may be some exceptions.