Technically speaking since the mobile carrier requested to the mobile phone maker that tethering be disabled by default on all phones for their network, then yes they are blocking a lawful, non-harmful service.
3 months is more than enough time to destroy any and all relevant evidence. anyone who thinks this is not possible or has already happened has their heads screwed on backwards. its way to easy to find out which hard drive the data in question is on and use a press to punch out the spindle of the hard drive and replace it.
"And Level 3 already showed at least with Comcast that there was some evidence that this was going on."
you are exactly right. this is the kind of thing that net neutrality was supposed to fix. as verizon would love for all of netflix's customers to just use verizon's video streaming service instead and part of how verizon tries to do this is by intentionally slowing down their customers traffic to netflix then blaming the entire thing on netflix.
looks like this is the beginning of the end. we Americans can only attempt to politely vote the worst of congress out of office so many times. if this passes i expect violent revolution from certain folks in this country.