Well, this new PS2 game seems to be running on the rumoured PS2 Shenmue 3 engine that Sega was working on for some time.
Since Shenmue 2 bombed on the Xbox (mostly due the console's continued pathetic sales in Japan), Sega decided to move Shenmue 3 over to the PS2. The engine got ported and tweaked quickly, but the next generation consoles would probably be out there by the time the game itself was completed, in traditional Shenmue-style long development times.
So, Sega decided to move Shenmue 3 to next generation and put together something less massive, with a smaller development time, on the existing PS2 engine (and maybe reusing some art assets).
This PS2 Shenmue engine seems to push a bit more polygons than the ol' Shenmue 2 engine, with better lighting and some glow effects. But in some close up shots the character's textures' resolution is surely not up there with the Dreamcast Shenmue versions'.