Are you sure he said wireless internet? I doubt it. If he did he may have misspoken. If your ballasts are putting out RF, I would be very surprised if it interfered with WIFI signals (wrong frequency). Why would a cable guy care about people's wireless networks, anyway? They are only responsible for the signal getting to your modem and the modem working right. Also, even if your ballast was putting out massive RF noise, there is no way that it could go far enough to interfere with 300 wireless networks (unless all 300 were in your basement or something), even if the noise was the right frequency.
What cable guys care about is the signal in their cables being degraded. The way this happens is that a source of RF noise leaks into their cables. This can degrade or even knock out the internet for a lot of people, including people much farther away than the range of the RF noise in the air. Although the noise may only have a range of a few tens of feet through the air, if a unshielded/poorly shielded cable is in that area, it will pick up the interference and conduct it through the cable, potentially interfering with people's internet farther away.
A way to think about it is that your ballast is a little radio station with a range of only a few tens of feet. There is no way that this could interfere with distant users. Now think of the coax cables coming into your house as antennas. The modem in the house down the street is too far away from the radio station (your ballast) to receive the signal through the air, so no problems. But, his modem is connected to the same cable network that comes into your house, the cable acts like an antenna, picking up the interference, degrading the guys internet far away.
So really, the problem is not that the ballast is putting out the RF, its that there is unshielded/poorly shielded cable near your ballast (within the small range of the noise from your "little radiio station") that is picking up the noise. This could be as simple as a cable that is not hooked up to something, or has a splitter with an empty side, or a poorly done splice, cheap cable with bad shielding, etc. Usually it is just that there is a cable that's not being used, or isn't screwed al the way into the cable box/modem etc.
It is also very unlikely that the cable co would say anything to the police. There are lots of things that create high frequency noise, and it is none of the cable cos business as to what you have at your house that is causing it. They don't care if you are growing. The care about the other customers bitching about their internet not working. Of course they would like to have your cooperation in fixing the problem, but you don't have to. If you don't cooperate with them, and they know the interference is coming from your house, they will just disconnect you, and their problem is solved. Also, if you think that a cable company's suspicions are probable cause sufficient to get a search warrant, you are too paranoid.
My advice would be to locate the cables in your house that are within 50 ft of your ballast, and make sure they are properly shielded/screwed in etc. Or ditch the cable and go satellite for tv and dsl for internet.
