No, if you are loading leaflet tile layers, it is not possible to change their style once loaded.
The key difference between your code and the example code you linked to is that the example code renders geoJSON data directly in the browser. Notice this line of code:
var featureLayer = new L.GeoJSON(); //... map.addLayer(featureLayer);
You are loading you data as a bunch of tile layers, which are pre-rendered .png images, and so can't be restyled in the browser.
With tile layers, all your data is first converted into small png images (either on a server, or locally with something like MapBox's TileMill) for fast load times and nearly no limit on data size; however as a raster source, you lose the ability to manipulate the data itself.
With feature layers loaded from a geojson, you reserve the ability to manipulate your data as a vector--style it in browser, run queries over it, etc--but loading even moderately sized datasets can become an issue.
If you want to be able to restyle your polygons on hover, look at using