I was simply implying that this game could have been made in any 3d engine (B3D and BMax included).
Here's a quote from the games wikipedia article which cites sources, explaining how the graphics came to be: The effect is achieved using a special Valve in-house rendering and lighting technique making extensive use of Phong shading. The game debuts with the Source engine's new dynamic lighting, shadowing and soft particle technologies, among many other unannounced features, alongside Half-Life 2: Episode Two.
So no. It most certainly couldn't have been done in another engine, because other engines cannot reproduce the stylized graphics, that make it work. The bottom line is, it's not the engine. It's the vision.
TF2 isn't really that visionary tho'. It doesn't really bring anything new to the table, it just does it really, really well. There's a reason it's called Team Fortress 2 you know.