Be careful with this. Importing the transit into your main personal calendar can create quite an overloaded calendar.
1) Login to Gmail or Google.
2) Create a fresh, empty,new calendar in your Calendar app. Then import the calendar ical/ics formatted file into that calendar. If you skip this important step, the calendar will import into your daily calendar. To undo that - you will have to delete the daily calendar.
By creating a new, separate calendar - you can control when and where you see it, and delete it easily if you need to.
You can add the calendar by choosing Import, and giving this calendar ID - don't import into your regular calendar. Create a new one and import to the new one.
6cc5217e0b8b6608554dace953ef316899ed915ded0340d685d4c77b2f32c3c2@group.calendar.google.com