I don’t think A is buying and selling like assets; but it is difficult to know for sure without further information. From the description provided it looks like the following is happening;
A is purchasing shares of a corporation (B Corp). Presumably A is purchasing the shares of B Corp because B Corp owns the rights to manufacture and sell Product C. So by virtue of A Purchasing the Shares of B Corp, A now has the right (through B Corp) to manufacture product C. The way it has been described it seems like a share purchase (shares of B Corp) rather than an Asset purchase, whereby A directly purchases the rights to Product C from B Corp or whomever owns the rights to Product C.
In an unrelated transaction A is selling the rights to Product D, which would seem to be a disposal of an intangible asset (possibly under class 14.1), which may attract recapture of CCA (formerly CECA) as well as capital gains on disposal.
It seems that Mr A might be purchasing shares of a corporation, but selling an intangible property, which would have no offset.
Furthermore, I believe under the rules that surround the new(ish) Class 14.1 (goodwill and other intangible property) the subsection 13(4) and 44(1) Asset Replacement rules (to defer recapture and capital gains) do not apply like they did with the old CEC Schedule. In order for the replacement property rules to apply, the former property must be a “real property” and intangible assets do not meet that definition. So, even if you are both purchasing and selling an asset that might fit into Class 14.1 I believe you would still need to calculate recapture and capital gain on the sale of Product D.