Firstly, the statute, I did not read about part 4 or go into depth in research about this matter, as a brief overview.
Important parts of section 5:
Section 5 (1)(b) states
Subject to subsections (2) and (3), a person shall not install, use, or maintain, or cause to be installed, used, or maintained, a listening device —to record a private conversation to which that person is a party.
Now for the exception to that rule that may apply to your situation...
Section 5 subsection 3) ‘Subsection (1)(b) does not apply to the installation, use, or maintenance of a listening device by or on behalf of a person who is a party to a private conversation if —
(c) each principal party to the private conversation consents expressly or impliedly to that installation, use, or maintenance;’
This could be proven if a sign is placed outside the shop or in clear view of the customers. This is because their continuance to shop or not expressly mention that they wished not to be recorded could be construed to mean acceptance as with the term consents ‘impliedly’.
Case law on this matter would more accurately describe how the courts are likely to view this argument and how impliedly is to be construed, but that is my basic assumption.
Subsection 3(d) has applicability as well. ‘(d) a principal party to the private conversation consents expressly or impliedly to that installation, use, or maintenance and the installation, use, or maintenance is reasonably necessary for the protection of the lawful interests of that principal party.’
For this subsection, if you can prove that your interests need to be protected and that your actions reasonably protect those interests, section 1(b) does not apply from my reading.
hope this helps break it down