How add IRB interface to SVLAN used for q-in-q

Hi All,

I have three ex-2300 switches and am required to carry any traffic from customer switches from one end to the other.

i have tested All-in-one QinQ set and it fulfills the requirement. 

i have 2 challenges:

1.  how to manage the switches from external mngt network. normaly i would setup mngt VLAN and attach IRB intefaces to it. with the QinQ setup, i cant attach irb to it as it says " l3-interface can only be attached to vlan with vlan-id/vlan-tag specified. 
2. will this setup allow me to run normal spanning tree across the switches.

attahed is network digram of how the three switches are interconnected.