You are able to use Machine Translation (MT) services on Transifex Native content as you do with all other content types coming from a specific file or through Transifex Live. In detail, Transifex makes sure that any placeholders are protected when you apply MT on that content, regardless of the service used (Google Translate, Microsoft Translator, AmazonMT or KantanMT).
In the case you are using MT fill up, the service will work as expected and described above, protecting any placeholders found on your content.