Sure it does, all the standard calls are universal, hell I wrote a _universal_ directory monitoring shell script. Try and do that with bash on windows/linux/osx.
If you're only going to use PowerShell functions and not external programs anyway, then PowerShell is more in competition with languages like Python, Perl, Ruby, etc., than it is with Bash.
PowerShell also falls down when it comes to the other distinguishing feature of a shell, which is that you gradually learn your scripting language just by using your computer, because PowerShell just falls flat as a daily login shell. This is mainly because it's unbelievably dog slow for a shell and lacks basic functionality like job control, but arguably also because of smaller things like its verbosity, extremely complicated profile sourcing behavior, etc.
PowerShell is still sometimes a good choice for cross-platform scripting, but I wouldn't say that's because of its compatibility.
That might be a good Show HN example.