I have no clue how an aluminum window is fixed to a solid block wall opening,I live in South Africa and the window I bought is glazed and came with 4 lugs that slides down the edges of the frame. The only thing I can assume is when the window is fitted,holes are drilled through the lugs into the masonry and fixed with some sort of anchor screw before being plastered.Well that's what I think I don't know
The basic thing to understand is that for stud wall structures there are two types of aluminium windows: one for new construction and another one for replacement in an existing structure. The two types differ in the outer rim which determines how they are fastened to the structure of the house. The difference in an installed window would not be evident from a casual inspection or even from a close inspection by a person who did not know what to look for.
Is your house a wood frame (stud wall) in which the brick is a veneer which only supports itelf. Or is your house a masonry construction without a wood frame?
OK so your building is masonry construction.
As I understand it the common way of installing modern windows in a masonry wall is to build a wooden frame inside the window opening and then fasten the window to that frame.
Depending on the type of window the window would be attached to the outer face of the wooden frame or to the "inside of the frame" outward, meaning not on the room side of the frame. If you have not done much carpentry, you need detailed advice. Local carpenters and builders in South Africa should be able to advise you.
Your assumption is right. You should fit the lugs to the masonry. As shown in this video at about 2m25s : https://youtu.be/bFsW1rh1r3I?t=145