Snatch: The Pokemon distracts their opponent at a crucial moment, stealing the effect of any healing, stat boosting, or supportive move. The opponent still pays for the energy cost of the Snatched move, but does not receive the effect. If it would be impossible for the Snatcher to fulfill the requirements of the supportive move (ex. not having enough HP to make a Substitute), Snatch will fail and suffer only its base EC cost. Snatch cannot steal moves used in combinations.
I feel like per the above, the third use of snatch would fail because subway already has a substitute so "fails to fulfill the requirements of the supportive move".
So matezoide: 100-27-35-11=27 en, sub 25, 88 hp
Jay: 100-24-28-32=16 en, sub 25, 50 hp
Idk man I'm as confused as you are but this makes sense to me
EDIT: I read (and I think deck might've too) read your sentence as can I snatch a sub if /I/ have a sub up
But jay's third sub 25 definitely fails and so I think snatch would fail too. I mean, he didn't MAKE anything for you to snatch away.