There are several different scoring systems and it will depend on the tournament.
The best source I can find describing the main scoring systems is webDiplomacy. On webDiplomacy, players ante points to play a game and then get awarded points from that pot based on their outcome, and so players are playing in a tournament-like setting for every game (unless they chose to play an unranked game).
Web diplomacy has three scoring systems, one of which is discontinued. They're described in full here: https://webdiplomacy.net/points.php
Here's the summary:
Draw size scoring: if you solo, you get all the points. If you draw, each player gets 1/N of the points, where N is the number of surviving players.
Sum of Squares scoring: if you solo, you get all the points. If you draw, each player gets points equal to
your_supply_centers ^ 2 / all_owned_supply_centers ^ 2.
Points per supply center: [discontinued] you get points equal to
your_supply_centers / all_owned_supply_centers regardless of whether a player soloed or it was a draw.
Anecdotally, I believe draw size scoring is the most common (I have a friend who has spent a lot of time playing diplomacy tournaments and insists that draw size scoring is the "true way to play").
Under draw size scoring (or sum of squares scoring), such a deal could make sense. The Italian player is gambling that the game will be a draw and they will get a piece of it, while the Turkish player is gambling that the Italian holdings will generate sufficient momentum for Turkey to solo. But if the game does go to a draw, Turkey would have substantial incentive to backstab Italy and get a larger piece of the draw, making this deal unlikely in practice.
I have heard of tournaments doing score based on what ordinal position a player finished in the game (1st through 7th) with player elimination time being the metric for eliminated players. Under such a scoring system, this deal could make a lot of sense, as it would allow Italy to generate an artificially high finishing position in the game despite being functionally irrelevant. The potential for gaming the scoring in this way is a big reason a diplomacy tournament should avoid using ordinal-based scoring systems.