Yes, you can manually set AdHandlerPlugin.PreferredBitrate (note: unit is bps) and it will be used to select the MediaFile closest to that bitrate.
If you always want the highest one, just set it to int.MaxValue
Note: The AdHandler plugin is an object you create in code or Xaml in your app. You can also access it via:
var adHandlerPlugin = mediaPlayer.GetAdHandlerPlugin();
adHandlerPlugin.PreferredBitrate = int.MaxValue;