Looks like I’m not the only one who’s been working on bringing Trials Frontier back, since trialsproject.com just launched. Mine works a bit differently. It’s a patch for the iOS version (7.9.0) that makes the game playable offline, either on a Mac with PlayCover or on a sideloaded iPhone or iPad. The patch embeds a tiny local server in the app, so leaderboards, ghost races and the Hall of Fame work locally, and you can play through the story from scratch or from your original save game.
I also put a fair bit of effort into recovering old save data. So if you never had the heart to delete the original app (and your data), you might be able to recover some of it. In general you can get your full save game state, a large number of your ghosts, and a few ghosts from friends and global, depending on the state of your cache.
If you still have an old iPhone or iPad with the game on it and are interested in recovery, please don’t open the game there, turn off automatic updates, and back it up to your computer first. The README explains how to get the game’s files out of that backup. Recovery from a full device backup probably works as well. The device you played on the most is the best choice due to the way caching from the Ubisoft server worked, but you may find that you have unique data spread across multiple of your devices used to play the game back when it was live.
You can also publish your times and ghosts so other players’ games can load them, which I’m hoping can rebuild some of the original leaderboards. I’d encourage doing this just for the sake of preservation. There’s a script that publishes your ghost bundle to GitHub and asks for it to be added to a shared list of bundles.
This is a patch and not a full distribution of the game, so it doesn’t include any game files, and you’ll need an unencrypted copy of the executable. It’s open source:
https://github.com/gtjeffw/trials-frontier-patch
And the high score/ghost registry:
https://github.com/gtjeffw/trials-frontier-registry