Hi,
Havnīt worked on A340s (-200/-300/-500/-600) without jettison so far. Neither have I seen an A330-300 with the system fitted; the 333 comes without centre tank, so max FOB is around 75t...
A330-200s can have jettison or not, it seems to be an option. Apparently, EK hasnīt ordered jettison initally, but then they bought an SB from AI (around 600 SB MHs, if I remember correctly).
I agree that fitting jettison probably goes along with a big difference between MLW and MTOW.
Cheers,
J.V.