Walked into new job with an active network.  There are two comm closet on the same floor that each have a 4510. The 4510's just have a management VLAN being trunked to a 6509.  Both switches are in transparent mode.  Both 4510's have the same vlan 300 (client end) but different subnets.  I was always taught to have unique VLANS for each subnet.  Not having any noticable network problems, just found this strange procedures.