No, it is completely different, more akin to the GT1 style used in TT's.

 

It's more than whats on the TT motor. They did share the 964 crankcase, until it changed to the spanish 996 case for builds started fall of '03. The TT motor does not have the same racing dry oil sump, nor the GT1 cam shaft, nor lightened pistons and valve assemblies, nor does it have titanium piston con rods. The GT3 motor is a work of art and costs $40K to replace. If the 997 GT3 is based off the M96 motor in the 997S... Unless they do some serious internal work to that motor, it won't approach that of the 996 variant GT3 motors, imo

 

I believe the TT also got the new Spanish crankcase. The TT's oil tank maybe different (larger) but it's the same system as the GT3.