QUOTE (Dakka Dakka @ Jun 12 2010, 11:25 AM)

I doubt that this is the intention of the rule, but by RAW, you are correct. BTW the wording never excludes the sustained spell contrary to the rule about threading, so whether the test involves the spell is of no import whasoever.
Just another point to Synaptic boosters for mages.
The main sticking point that I have with the idea that sustaining Improved Initiative applies a penalty to every test besides the initial Spellcasting roll is that the spell isn't being sustained *before* you cast it. The sustaining penalty can only exist
after the spell is successfully cast.
Perusing just the main book, here are spells that act oddly if the penalty for sustaining them applies to them:
Analyze Device (SR4A, p.206): effective Threshold of this spell is Object Resistance +2 in order to suffer no penalty while using the device. For virtually anything that counts as a "device" you need to cast it at at LEAST Force 6 in order to ignore the penalty for defaulting. Awesome.
Combat Sense (SR4A, p.206): effective Threshold of this spell is 2 in order to get *zero effect* (as it adds to defense tests while active)
Increase Attribute (SR4A, p.208): gains an effective Threshold of 2 in order to get *zero effect* when the caster uses it on himself
Increase Initiative (SR4A, p.208): effective Threshold of 3 in order to get *zero effect* on Initiative rolls. (I won't deny that extra passes are always good, obviously)
Oxygenation (SR4A, p.208): effective Threshold of 2 in order to get *zero effect* to the listed tests when the caster sustains it on himself
Prophylaxis (SR4A, p.208): effective Threshold of 2 in order to get *zero effect* to the listed tests when the caster sustains it on himself
Armor (SR4A, p.210): effective Threshold of 2 in order to get *zero effect* on damage tests involving Ballistic or Impact armor.
(Side note: AS WRITTEN, it seems that *every* sustained spell inflicts a -2 penalty on Damage Resistance Tests -- which seems rather brutal to me, but...that's what they
wrote).
Levitate (SR4A, p.210): effective Threshold of 2 in order to get *zero effect* when hurling Levitated objects at targets. There's also (arguably, though petty) an effective penalty of 2 successes in the opposed test to levitate either an object being held by a living being or an unwilling living being (both cases are an opposed test pitting F x 2 vs STR+BOD
Magic Fingers (SR4A, p.211): effective Threshold of 3 in order to use the spell *as written* with no additional penalty
Shapechange / (Critter) Form (SR4A, p.211): effective Threshold of 2 in order to use the spell *as written* with no additional penalty
On top of that, the assumption that the *only* test involving a sustained spell that is exempted from the penalty for sustaining it is the Spellcasting test (that occurs *before* sustaining the spell) means that willingly passing through a Mana Barrier while sustaining spells is beyond foolhardy (as you suffer a crippling penalty and *still* need to get 1 additional success for each sustained spell you want to bring through), while someone sustaining the same number of spells who is either forced through a Mana Barrier or walks through one unawares has a much easier time.
Using the stock Combat Mage (SR4A, p.99) sustaining a Force 5 Armor, Levitate, and Increase Initiative, here's the difference:
WILLINGLY WALKING THROUGH A FORCE 5 BARRIERThe Combat Mage rolls Magic (5) + Charisma (4) - 6 (three sustained spells) versus Force (5) x 2, or 3 dice versus 10. AT BEST, said mage is having one spell disrupted (as he can only roll 3 dice)
UNWILLINGLY OR UNKNOWINGLY WALKING THROUGH A FOCE 5 BARRIERThe Combat Mage player rolls Force (5) x 2 for each spell versus Force (5) x 2; even money for each spell (and far more likely for all three to make it through). Of course, I assume that the spells roll their full pool (since it's not the *caster* who is defending), but a particularly strict/obtuse reading might demand that the penalty for sustaining be applied...which is STILL likely to be better, as the spell is rolling 4 dice versus 10 rather than 3 dice versus 10 -- and there's an (albeit unlikely) chance that *every* sustained spell will make it through, versus the GUARANTEE that only two even CAN. (Plus, regardless of the outcome of the spell tests, the caster who is inadvertently/unwillingly walking through is getting through regardless of the rolls...assuming that he doesn't have the mis-fortune of Astrally Perceiving (and thus dual-natured) while somehow going through the Barrier unwillingly/unknowingly.