Communication wiring installer?
Except for, perhaps, up to ten feet of pipe to provide power to his equipment, I'd expect the installer to pretty much limit himself to Cat 5 and Coax (or similar wire types). MAYBE speaker wire.
Now, if the installer represented a particular product ... Muzak, some intercom line, etc., I'd expect him to have the materials unique to those products.
If his work moved him into materials and methods not commonly used - such as running pipe - I'd pay particular attention to the work performed. "Specialty" contractors seem to limit their code compliance to their specific few paragraphs