STO according to the wiki, recognises "pieces of" Destiny, pertaining to commandra Donatras romulan power struggle, but chucks the rest.
Modification: Sorry, i meant Titan series, although they crossover. Anyways, In terms of The canon, My opinion has mutated to the following: we can argue and debate forever on whats recognsied or not asd canon, The pocket books Destiny series may have been" allowed to be" written, But Janeways own backstory on what was her first ship was "supposedly" clearly stated in a novel and disregarded and overthrown by an episode of Voyager, paramount has a habit of giving the green light to media then sayign F*** em well do this and contradict it anyways. So yes, even STO "must" by logic, be treated the same as the books- not canon-because like bridge commander/armada 1 and 2, SFC 1-3, the "stories" are like glorified fan fic- Tim russ<Tuvok">helped make "of gods and men" with many trek alumni, but does this give credit as canon to it? Unfortunetly not.
The exception to this rule in furthur common sense, is the canon of "countdown", because it was written by michael ocri of the Trek V! film, as a prequal backstory, an "extention" of the films plot, he recognises this by his own pen to paper as what happened in TNG era 2387, so use common frikkin sense- its close enough to be a "child" of the film in "prime" trek no less- to be treated as canon.