interpretation of section 158BB(ca)

[scaa]

The clause states that where due date of return has expired and no return has been filed,returned income is considered as NIL. In case an assessee (158BD) files return after the date of search but before the date of notice issued under section 158BC read with section 158BD, My questions:
a) Does it imply that the return has to be filed at least before the date of the search ?
b) In case of a 158BD assessee, would the date of search be relevant or the date of notice issued u/s 158BC read with section 158BD be relevant?
c) Should the return have been filed only within the date ?