Alister is 9-C, Thomas is 9-B to 9-A.
So despite Allister's tier & the restriction on his Pokemon, this small boy's encounter with a train will probably involve a ghost nonetheless.
Albeit, in a perhaps rather fittingly posthumous manner.
Allister's best hope depends on speed being equalized to a low enough value that he can get to the side of Thomas (If Thomas has to be on rails/traintracks in this, better yet.) & hoping he can get on board.
Presuming he does that, Allister just has to stay on board Thomas while this sentient train tries to kill his passenger, & last until Thomas runs out of fuel, becoming unable to move & further harm him.
If Allister does get on board, Thomas's best option is probably to make wild veering, movements to tilt Allister's footing & hope he falls out, at which point, it becomes a balancing game; Ideally, Thomas will make a sharp enough turn with a strong enough jolt that Allister will lose his grip on whatever he's holding onto (Does Thomas have a whistle string? Handlebars? Doors to close? Furnace door?) & be flung out or ram into a wall.
Or he hopes Allister becomes exhausted.
Either way, it probably comes down to stamina & who's able to handle the movement more capably, since making wild tilts & turns that risk him crashing is probably around the same level of risk for Thomas as it is for Allister's life, except Thomas is Small Building Level to Allister's Street Level.
So yeah. How's their maneuverability & intelligence for this? Would Allister think to get on board Thomas? (He's trying to defeat the train after all.)
Would Thomas think to go wild if Allister got on board him?
Oh & obviously, there's the possibility that since Allister's standard equipment, Dusk Balls work on sentient trains, Allister just catches Thomas, GG, assuming Thomas can't break himself out after being caught.
Dusk Balls work better at night time & in caves. What are the circumstances, & how are they affected by SBA here?