My T9 has a shield for defence (boosted biweave) and has survived every attempt by CG campers to kill it. Admittedly I've made to the station with with hull in single digest percentage more often than I'm comfortable with but I'm still delivering >700 tonnes every time which consistently got me 10% finishes in CGs.
It's not impossible and possibly more important than any amount of armour is being aware of your scanner and spoiling the would be gankers aim before you you're ready to wake.
Yep, properly defended and aware T9 is very hard to kill for single attacker, thats it, because, if T9 owner would loiter long around for a full wing of pacifer P2 to drop on such, then even hi-wake would not be enough. But luckly for anyone who is attacked by full wing, getting full wing into instance within short amount of time, can be tricky for attackers, as by time full wing drops, T9 is about to finish charging its FSD, if followed proper steps and being well aware what is happening.
Another thing that full wings (4/4) usually are busy with other things than single targets, so its actually quite rare to find such, and even more rarer to end up being thier target, mostly because.. of instancing, especially if cmdrs who are in wing, are from all over world, literally... and if just one of them have any connection problems or lag, then entire wing is affected. This all gives all required time that any attacked cmdr needs, to wake out of such "problem", especially after interdiction.
But some smart cmdrs knows this and they are usually hi-wakin right in about very moment when wing drops on them (once realized that full wing is after thier ship). Thats situational awarness that only some cmdrs have, since thats what makes big diffrence to fly away or eat rebui.
Shields always lasts few seconds, but then there is plently of armor left, and that usually last to for T9 making that wake out. Bi-waves main advantage over any other kind of shields, that is these can deny chain-interdictions. As when such happens, bi-waves are usually back online, if fallen, by the time next interdiction ends.
T9, if not mass locked, can easly low wake out from smaller ones, and if mass-locked by conda or cutter or vette, or if attacked by a wing then hiwake with equally ease....
On top of all above, if T9 owner didnt slept on MRP's and have things like armoured FSD and plant, I'd say these can make diffrence too, but that all apply preety much to any ship, not just T9's. Armoured plants and especially FSD - along with some MRP's can make such diffrence that ship might well as run out of its hull points first, than being planted or FSD sniped out. Weakest spot of all T9 are its thrusters (quite durable on its own - its size 7 after all), but long as there is dual MRP in bulid, then drives will not go down before both MRP would.