Great question!
If using Swiftype’s web crawler, the ability to fetch the respective custom meta tags will require them to be viewable within a static HTML page. If your SPA generates an HTML proxy for each page instance, and those pages are able to be detected by the crawler you should be good to go. There’s some additional info in this thread.
The other option would be to build out your engine with our developer API in order to create unique result documents.