Your iPhone has the capability to plan trips on MTS Trolleys and Buses built-in to your Maps app. Here's how to plan trips on MTS (and all other participating transit agencies world-wide).

First, open up your Maps app and select Directions at the bottom of the screen. 

Type in your starting and ending locations and click on Route.

You will receive directions for your route. To get transit directions, make sure that you press the bus icon.

Your route is shown on the map.  If you press Start, the transit directions will be shown step-by-step.

You can change the date and time of your trip by clicking on the Clock icon.

If you want to see a list of text directions, click on the settings reveal button in the lower right corner and select "List".