Bet your ass. Why do you think he's so eager to get off this rock?
More generally,
how do you think he knew how to summon the Scrin? He must have known they'd be attracted to liquid tiberium explosions, either by reading that information off the Tacitus during Tib War II, or from some other source.
Which in turn means he must have at least a rough idea of what liquid tiberium explosions occurring in nature imply- that a planet is in the process of being blown apart by tiberium.
And if he didn't know that, he must have figured it out after capturing the Threshold tower, because the tower's ability to go out of phase and its internal equipment would lead logically to a mind like Kane's considering:
"What environment is this tower designed to survive, that requires such defenses?" Normal Scrin buildings don't have invulnerability phase shields, and yet are perfectly fine in Red Zones or even in direct contact with tiberium as far as we know. The Scrin must clearly intend to go on harvesting resources on a planet that is in the process of being outright
destroyed, or it wouldn't be worth bothering with the invulnerability.
Do GDI and NOD even know about that time bomb?
GDI can calculate its existence. We know enough about tiberium. We know it's going underground. We know enough about liquid tiberium to know it naturally forms from tiberium under certain conditions, and that it would go 'kaboom' on contact with magma.
I suspect there's still some scientific uncertainty, so Treasury experts aren't yet proclaiming it... But I'm pretty sure the knowledge is there.
Nod as a whole, as distinct from Kane? Dunno. Hard to say.
For all we know getting the mining tendrils done increases the efficiency of the Vein Mines significantly. Vein Mines is, more than anywhere else, where that tech will have the most impact imo.
I've speculated the same myself, because it so vastly simplifies the mining process- but we'll see. A lot of the stuff required for vein mining wouldn't be simplified that much, and the mining tendrils themselves are
really expensive, what with finicky STUs and xenotech integrated in to replace what was once a big uncomplicated steel sweeper arm and a box.
Ithillid was talking about the underground Tiberium deposits. We don't have any kind of effective way to deal with the Tiberium burrowing its way through the Earth's crust and towards its mantle. Even if we did tons of Tiberium Vein Mines, there's way too much Tiberium that's too far deep underground that we can't get to at all.
What we can do, theoretically, is clear the surface of Tiberium. It wouldn't stop the Earth from exploding eventually when Tiberium converts the mantle into an ocean of liquid Tiberium, but it would buy us decades of time in order to evacuate the planet and/or build a TCN. (If we ever get the plans for creating a TCN, which isn't certain by any means.)
The deep underground Tiberium is a slowly ticking time bomb that our mitigation can't touch. But the surface Tiberium would have killed us much, much faster if not for our conventional mitigation efforts.
You're not wrong, though if we went
really ham on trying to get down and dig up subsurface deposits it might buy us some more time. Ithillid mentioned "tiberium boreholes," which I imagine are the next logical step after completing some insane amount of vein mining. That might help a bit.
But sooner or later, we'd miss a deposit deep down in the crust, liquid T would come into contact with magma, and
boom.