This isn't an argument for privatization, but the proposal from the OP are not the same as full an open free market. You still have the USPS responsible for ensuring delivery to the long-tail routes. That just gets bid out (probably at a higher cost that delivery occurs for today). These are the kinds of bids companies like Halliburton take.
I'm not in favor of this approach, either we have a really free market (with some limited regulation for things like anti-fraud) or you have the government manage the service. These public-private partnerships just seem to be grift programs write large. Let's not push for more corporatism. If there is already a private market, then sure, have the government bid for private contracts within that market. Otherwise you have companies whose full-time roles is figure out how to squeeze more money out of government, and they lobby hard to do so, often with much success (at filching taxpayers)
I'm not in favor of this approach, either we have a really free market (with some limited regulation for things like anti-fraud) or you have the government manage the service. These public-private partnerships just seem to be grift programs write large. Let's not push for more corporatism. If there is already a private market, then sure, have the government bid for private contracts within that market. Otherwise you have companies whose full-time roles is figure out how to squeeze more money out of government, and they lobby hard to do so, often with much success (at filching taxpayers)