I have found that I can get extended VLANs to propagate with VTP using version 3, but I noticed that it still does not prune extended VLANs. I tried to add an extended VLAN to the prune eligible list but received an error:
CAT_3750-48-TS(config-if)#switchport trunk pruning vlan 1120 Command rejected: Bad VLAN list - character #5 (EOL) delimits a VLAN number (1120) out of the range 1 to 1005. CAT_3750-48-TS(config-if)#
Is there a way to allow VTP to prune extended VLANs? If not what is the point of supporting extended VLANs to begin with?