I'm not entirely sure I understand the question. If I'm understanding right then yes, if they were non-cross class before the class, then you can add ranks to them as class skills.
Yea, knew it was unclear when I wrote, but couldn't think of a better way to write it at the time.

That is the answer I was looking for, I think. To give an example, an Immortal taking a level in fighter can put a point in, say, use magical item as though it were a class skill