I love how your telling me it can't happen, when it happened to me not but a few months ago. Radio frequency travels back through your cable wires if they are old or unplugged at the floor but plugged in at main. This is an extremely common issue with digital ballast, not something new.
The cable company is not there to cause you any problems, or rob you, or are cops. Come on man. You do not have to allow them access, even if they ask. Simply say "no, I'm not comfortable with strangers in the house, can you do what u need from the outside, and instruct me what to do on the inside". They guys that come out have a job to do, if they don't do it they get in trouble with their boss. rfi effects way more than just cable and internet.
Your electrician friend and yourself should research further into it. You can tell him to get a EMF meter and walk around a grow room. Your ballast, mini splits, dehumidifier, blue lab guardians or trimeters all put off rfi. Put it on the wires at the powerbox for those equipment on 220, it'll go crazy.
Rfi is real, and it's also real easy to deal with.