Utility companies won't hold the coin. This starts the leaky ceiling as to how much the Utility company accepts and sells vs how many claims get sold off vs how much PoW coin drops the price.
Hope it works out though, and at least it is a step in the right direction if the market supports the sell offs.
I hope a utility like ekWateur will hold SLR as much as possible, they appear to be ideologically aligned with the concept and (again I hope) they believe the future price is worth waiting for. Most of us probably cant pay for our electric bill in full with our current SLR claim, so ekWateur wont be flooded with SLR, they will get a slow trickle, meaning its just a marginal amount for them that they can afford to stash.