Try this:
function Test-ReparsePoint([string]$path) {
$file = Get-Item $path -Force -ea SilentlyContinue
return [bool]($file.Attributes -band [IO.FileAttributes]::ReparsePoint)
}
It is a pretty minimal implementation, but it should do the trick. Note that this doesn’t distinguish between a hard link and a symbolic link. Underneath, they both just take advantage of NTFS reparse points, IIRC.