Thanks for your question! It hasn't been directly addressed, though it gets touched on a little when the AC Bonuses are granted. Usually when I grant a request, I give a quick rundown of how the items arrive.

Generally, the perks are not an IC concept. Characters shouldn't be trying to "save up" for new powers or an item from home or anything, they simply know that the more they try to become part of the society, help protect the city, and otherwise contribute, the more likely they are to get nice things through the portal.

The IC explanations for how characters get more complicated things like powers or locations from home, things that can't just pop through the portal, are varied, and usually case-by-case. You can find an example of how I have granted a canon location here. For powers, I haven't specified anything, but generally it is assumed that living in an alternate reality that is not your own can affect how your body functions, or they could receive it through a player plot, via a found artifact, or...well, basically anything else. If a player has a specific idea for how their character receives the power, or if they just want to handwave that it shows up one day, I'm fine with either and I can work it out with the player in question!

I hope this helps and isn't too vague! Feel free to ask more if you need to.