There might be a way... You can't build a "regular" template. Your best option is to build a generator, one time use for each video, but you can use the first one you build and "replenish" the list for each subsequent project.
This project is mostly about creating subtitles that are animated in a repetitive scrolling animation. (It's not that hard, just bear with me.) If you don't have a lot of titles to do, it might just be faster to create the individual titles in FCPX with the template you've already built. The following project might be easier in the long run though... it's worth knowing.
Part 1:
You will need to know how long your video will be, and it will help if you have the soundtrack exported from your cut video to aid in timing.
If your video is 20 minutes long, create a project in Motion that is 20 minutes long. If you're reusing the "template" for other projects down the line, you can adjust the length of a saved project by selecting the Project "layer" and in Properties, set the new time length in the Duration parameter.
Type out a list of song titles in a TXT file (TextEdit will do fine, but use plain text only -- the file type must be TXT.) Every song title must exist on its own line. Start with a blank line (you need it to keep a blank until the first title is ready to "play".)
In Motion, you can use a Generator > Text Generator > File Generator. In the inspector, Browse for your txt file. Set the Speed to Custom (the default will have the custom speed already keyframed from 0 to 100%.)
At some point, add your sound track (you will delete it before you save the project - you won't need it and it's just dead weight in the Media folder.)
Listen to the soundtrack and when the song changes, increase the Custom Speed by enough to change the title. (A shortcut would be to watch the audio waveform for "silence" — just move the playhead to those points, etc.)
When you've created all the keyframes, you need to open the keyframe editor and select the Custom Speed parameter in the left column. When you mouse over the line, you'll see a small disclosure triangle appear on the right edge - click on it and select Interpolation > Constant. All the keyframes will become "step-wise".
Part 2:
Format your text like you want it to appear in your video. Find the longest title - that will determine your spacing in the titles.
Clone the Group containing the File generator (it's just tidier that way... no other real reason.) In this **rare** occasion, duplicate the clone layer. Move the duplicate to the right and leave just enough space between the two versions. Make a note of the distance you offset the duplicate -- you'll need it later. Create a Rectangle, Fill (any color), no outline— that will be your "window" (mask) for the text (it doesn't matter if it's a little less wide than the song title) and create a small negative feather. Turn it off for now.
Select the Group containing the two clones and type the L key to create a Replicator. If the group containing the File generator didn't turn itself off, you can uncheck it in the layers list.
Set the Shape to Line and the Points to 1. (It might help to set the Start and End Point Xs to 0.)
To the Replicator add Behaviors > Replicator > Sequence Replicator.
In the Behaviors tab for Sequence Replicator, Add > Parameter > Position. Move the Playhead to the start and set a keyframe on the X parameter. Move the Playhead however far you want the titles to pause (15 frames or a half second seems a good starting point) and set another keyframe. Move the Playhead to the 3 second mark and type in negative offset distance between the two clones (you can make adjustments to the ending keyframe in the keyframe editor). Set Sequencing to "From Keyframes" and set Loops to about 20 for every minute of play (I think... You may have to adjust this later.) If your video is 2 minutes, set 40, etc...
To the Group containing the Replicator, right click on the group layer and select Add Image Mask and drag the rectangle you drew into it. (Just for "neatness's" sake, drag the rectangle into the same group as the replicator.)
Ok - at this point, I think that's everything.
Delete the soundtrack and Save the generator to FCPX in a category specialized for this type of effect ("Subtitles" maybe?)
Go back to your video project and drag the generator onto the project. Playback to check/adjust the synchronization (it should be exactly synchronized from whatever point you exported your audio soundtrack.
When you're completely done with this project, you can delete the generator from your Motion Templates / Generators / <chosen category> folder or reuse it for another project (rename it too!) You'll need to do the same adjustments for title length and to the Sequence Replicator if you have to change the distance between the two text clone layers, but once you get this down, it should be easy to put together again.
HTH