It doesn't really matter who damaged it or what it costs. It was damaged on company time/business, and it sounds like the company has admitted this, even if they don't know how they did it. They should be thankful that you've been providing such an expensive tool paid for out of your pocket.
If they owned them they'd need to replace them, and then they would have paid for them twice. This way they only need to pay for them once.
You break it, you buy it. If it's acceptable to you, perhaps buying a used pair in equal or better condition AND having them sent out for calibration would save them some money, though likely not a ton and you might end up with a worn out tool.
I don't like getting up in a wad about things, but if someone blatantly damaged my property without owning up to it and making things right I'd be removing myself from the environment at my soonest convenience (IE as soon as I lined up another job).
I've accidentally broken or otherwise ruined more than my fair share of tools borrowed or otherwise in my care over the years. All of those people/entities are willing to loan to me again because I made sure they were whole before I was done. Sometimes things were repaired and returned cleaner than new, others they were replaced with an equal or better item of their choosing. The only question that ever came up was if I needed to do both (a quick repair because it was needed ASAP and an eventual replacement to make it right long term).
