How to use MsBuild MsDeployPublish to target local file system?

As per my answer from Using MSBuild, how do I build an MVC4 solution from the command line (applying Web.config transformations in the process) and output to a folder?

msbuild ProjectFile.csproj /p:Configuration=Release ^
                           /p:Platform=AnyCPU ^
                           /t:WebPublish ^
                           /p:WebPublishMethod=FileSystem ^
                           /p:DeleteExistingFiles=True ^
                           /p:publishUrl=c:\output

Or if you are building the solution file:

msbuild Solution.sln /p:Configuration=Release ^ 
                     /p:DeployOnBuild=True ^
                     /p:DeployDefaultTarget=WebPublish ^
                     /p:WebPublishMethod=FileSystem ^
                     /p:DeleteExistingFiles=True ^
                     /p:publishUrl=c:\output

You can also target the project via the solution using the /t:SolutionFolder/Project:Target syntax:

msbuild Solution.sln /t:SolutionFolder/ProjectFile:WebPublish ^
                     /p:Configuration=Release ^ 
                     /p:WebPublishMethod=FileSystem ^
                     /p:DeleteExistingFiles=True ^
                     /p:publishUrl=c:\output

I gave up trying to get MSBuild to copy deployable web files (and not do anything else but that), so I scripted it in PowerShell and am really happy with the result. Much faster than anything I tried through MSBuild. Here's the gist (literally):

function copy-deployable-web-files($proj_path, $deploy_dir) {
  # copy files where Build Action = "Content" 
  $proj_dir = split-path -parent $proj_path
  [xml]$xml = get-content $proj_path
  $xml.Project.ItemGroup | % { $_.Content } | % { $_.Include } | ? { $_ } | % {
    $from = "$proj_dir\$_"
    $to = split-path -parent "$deploy_dir\$_"
    if (!(test-path $to)) { md $to }
    cp $from $to
  }

  # copy everything in bin
  cp "$proj_dir\bin" $deploy_dir -recurse
}