They certainly weren’t given cash like the french government is doing. The most you can say is that Bell Atlantic, Verizon’s predecessor, was allowed to accelerate depreciation of their copper network more quickly than under the previous tax rules.[1] Whether that amounted to a subsidy depends on how quickly the value of the copper plant decreased after fiber was built. The accelerated depreciation was based on the quite reasonable assumption that the value of the copper network depreciated more quickly after fiber was built. I’ve never seen a calculation refuting that premise.

[1] When you build an income-producing capital asset like copper wire in the ground, you can’t deduct the cost from your revenues immediately for tax purposes, like you can with say employee salaries. Instead, you gradually deduct the capital cost over the income-producing life of the asset. If the government allowes you to depreciate an asset faster than the value of the asset actually drops, that nets you some tax benefit due to the time value of money. On the other hand, if the accelerated depreciation reflects the fact that certain types of assets depreciate quicker, then it will result in the correct amount of taxes being paid. For example IT equipment in data centers can generally be written off immediately—unlike wires in the the ground it’s pretty much worthless after a few years.