Where the BSA directs the Court to “shall presume” a fact, what is the effect of that mandatory…

Section 2(1)(l) defines "shall presume" to mean "The Court must regard the fact as proved unless and until it is disproved". Calling for proof belongs to "may presume" in section 2(1)(h), so "The Court may instead decline the presumption and call for proof of the fact" is wrong, and conclusive proof under section 2(1)(b), which excludes disproving evidence, is described by "The Court must treat the fact as conclusive and prohibit evidence disproving it".