I believe it is called a merger.
Since they are, you know, merging.
The products are irrelevant to the merger (though probably not from the inside decision making process) as it is not the products that are merging but the companies.
"Collusion is is an agreement between two or more persons, sometimes illegal and therefore secretive, to limit open competition by deceiving, misleading, or defrauding others of their legal rights, or to obtain an objective forbidden by law typically by defrauding or gaining an unfair advantage." Webster's Dictionary