I assume you mean they have 3 way 3 phase transfer equipment.
If this is corner grounded I don't see a reason to even have a "neutral" from either generator it is one of the phases. The service grounding point (MBJ) and the corner ground in each generator would suffice to ground the service.
If you center tap ground this, then you do need to deal with the neutral somehow. (SDS/non-SDS rules)
edit
In fact if this is corner ground and you "float" the generator bond, you could bolt the grounded phase (white wire) and use 2 pole transfer equipment.
