"Times have a changed" When I got out of College I started working for a two way radio company designing, installing, maintaining and repairing two way radio equipment. I had to have an FCC Class 1 or 2 License to even touch the equipment. A few years later you could get a NABER Cetiricate (Now PCIA). The FCC license and NABER Certificate was the only way you could do the work and if the FCC audited the company and found non dertified techs working on equipment, the Company was fined not the employee. In addition the employer could take no action against the employee. Once ther FCC no longer required the license or certicate the industry went to hell. The FCC should go back to requiring the license or certificate for all communication equipment. This would give the installer at least some standard to follow.
On another note if you have the certificate of insurance with a hold harmless clause there is no pecking order. You are held harmless and not responsible. You could also have an inidemnification clause that will remove all responsisbilty from you.