flat plane crankshaft on v12 engine

It's not necessary (nor desirable) to use a flat-plane crankshaft in a 12 cyl engine with two banks of cylinders. The "advantage" that the flat-plane crankshaft gives in a 90 deg V8 engine is that it results in alternate bank firing of the cylinders -- so the time between each exhaust pulse entering the (shared) exhaust manifold in each bank is the same. The non-flat-plane crankshafts that Ferrari uses in all its 12 cyl engines also gives the same desirable alternate bank firing of the cylinders (but they are not "cross-plane" crankshafts because the crank throws are grouped 60 deg apart, not 90 deg apart).

 

Can't say that I've ever heard a specific name associated with the crankshaft configuration that Ferrari uses in their 12 cyl engines -- here's a pic of the TR crankshaft (but I believe all the 12 cyl F use the same general crankshaft shape as far as the throw positions are concerned):

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Another factor that Designers have to consider when selecting a crankshaft design/firing order is the peak loading on the main bearings -- using the flat-plane crankshaft in a 90 deg V8 engine has a bit of a negative in this regard so the bottom end structure has to be stronger than the bottom end structure of a similar hp cross-plane crankshaft 90 deg V8 engine.