I found out that replacing
$this->docRoot = isset( $this->options->doc_root ) ?
$this->options->doc_root : $config->docRoot;
$this->docRoot = str_replace('/', DIRECTORY_SEPARATOR, isset( $this->options->doc_root ) ?
$this->options->doc_root : $config->docRoot);
in Process.php fixes the issue. You have to un-normalize the path otherwise it is looking for filepath such as C:/MyFolder/MySubFolder/etc/... instead of C:\MyFolder\MySubFolder\etc...
Issue #42 (@import don't work under Windows using cli.php)
Additionally the --context option was casting to array (typo).
Thanks for reporting this.
I've pushed a fix to the test branch. Also fixed another bug in the process so will likely be pushing a patch release soon.