Spirit Power - Aura Masking, what spirit can get it? Options

[Stahlgewitter]

Hoi Chummers

ive been tweaking my Possesion Mage and found Aura Masking in Street Magic

SM:
New Spirit Powers
The powers listed here are in addition to the normal critter
and spirit powers found on pp. 286–291, SR4.

Aura Masking
Type: M • Action: Free • Range: Self • Duration: Sustained
This power functions as both the initiate powers Masking
(p. 190, SR4) and Extended Masking (p. 60). The spirit uses
its Edge in place of initiate grade. The spirit can also hide the
use of any of its powers on itself within the masked aura. Only
characters who pierce the masking can see the spirit’s use of
spirit powers on itself. A spirit can always attempt to appear
as another form of astral creature (even if not capable of astral
projection), but masking itself as mundane would be entirely
pointless unless it is joined to a physical body or has the realistic
form power.


but no premade Spirit has this power, or can to choose it as optional power.

So now i would like to know if i can give it my Ally Spirit?
Do i have to learn Masking and Ext Masking to give it to him?
Or can i simply choose it at Ally creation (which in my case would be char creation)?

Cause i plan to get only possessed from my Ally and if i can learn him this power from character creation i could learn
masking+ext masking a lot later, which would give me more room for other stuff (IMG:style_emoticons/default/smile.gif)

Also is there a list which Powers an Ally Spirit can learn?
cause i am interested in a few other to ^^