While I don't consider myself a libertarian by any stretch, typically roads and utilities are two of the things that have pretty easy counter-arguments - make utilities free market (or something of the sort) and roads can be paid via tolls.
If you want something that doesn't have a good counter-argument, look at policing and contract enforcement (basically, a public legal system). That's something that can't be done very well by a private entity or multiple competing private entities.
Another problem without much of a counter-argument is looking at e.g. utilities and roads together (i.e. a monopolistic infrastructure with a non-monopolistic infrastructure). Roads are monopolistic because they control that land - in order to use it, you have to pay the owner what they want. This isn't too big of a problem because if you feel one route costs too much, you can simply take another route. Utilities on the other hand, can be provided by anyone, as long as they run the pipes, lines, etc. out to you. In itself, if you feel one utility costs too much, you can pick another utility. The problem comes with combining the two - typically to deliver the utility to you, they would also have to pay the road owner to run the lines along and/or make some agreement. So what happens when an exclusivity agreement comes into play?
Well, unless you don't want the utility at all, you have no choice but to either pay whatever fee they want you to, or move. When you move, it's possible an exclusivity agreement exists there too. One could argue that it's not any better the way it currently is (Comcast, etc.) however you couldn't make it better by making everything privately-owned without regulation, and you could make it better by going further towards the public side.
Forking isn't possible when the code is not there, and when the company that created/copyrighted the code is openly hostile to forks. By them releasing under MIT, this issue is resolved.
As for the manpower behind Microsoft, git has made it very easy to merge code from relatively similar source code - in the cases that they make large important changes, those can always be merged in, and usually without too much work involved.
The only way they could succeed with something like that would be for them to go closed-source again, in which case you're still better off than if they never went open in the first place because you still at least have some code to work from.