From what you describe, it appears to be compliant. However there may be an issue with fill capacity.
As to a label, IF you are under the 2011 NEC (312.8 (3)) a warning label as to the location of the means of disconnect for ALL the conductors must be posted.
Based on the (3) verbiage, said label will indicate that multiple sources of power are present, although another label stating 'multiple sources' would be a prudent item.
As to the quality of the workmanship.....here in NJ, I cannot fail for that; however there may be other things upon performing a compliance inspection.
Reading your last comment regarding that this is a 'life safety system, yes a flash incident will be a problem.
Was this a designed plan job, or a seat of the pants job??