Do the Borg have non-aggression pacts with more advanced species, with the queen or other kinds of Borg hierarchy acting as spokesperson?
Out of canon, yes we do see an instance of the Borg forming an alliance: with the Cybermen.
The comic book crossover series Star Trek: The Next Generation - Doctor Who: Assimilation involves a plotline in which the Cybermen of the Doctor Who universe alter time in order to form an alliance with the Borg.
Whether you consider the Cybermen to be more advanced than the Borg is another matter.
It appears not.
From Q Who?, arguably from one of the more knowledgeable in-universe sources:
PICARD: How do we reason with them? Let them know that we are not a threat?
GUINAN: You don't, at least to my knowledge nobody has so far.
And later on in that episode:
GUINAN: Your contact with the Borg came long before it should. When you're ready, it might be possible to establish a relationship with them, but now -- now, you are only raw material to them.
This could mean that she thinks the Borg are more diplomatic towards more dangerous or more advanced species, or just that a stronger Federation could force a truce or peace with sheer power.
While not technically with a more advanced species (though they did have an advanced weapon) the Borg formed a temporary alliance with Captain Janeway (Voy:Scorpion) against Species 8472.
From Memory Alpha (emphasis mine):
Janeway ordered Voyager into System D43119, an assimilated star system, and began negotiations with the Collective, intending to offer The Doctor's research as tactical data about its enemy, in exchange for safe passage of Voyager through Borg territory. She had all of the data put into The Doctor's holomatrix; she would have him deleted, and the data along with him, if the Borg tried to assimilate Voyager. An agreement was reached; the Borg would escort Voyager through their space, and, while en route, Voyager personnel would assist the Borg in crafting the research into a biological weapon...
Once the invasion had been repelled, the Borg promptly terminated the alliance with Voyager and attempted to assimilate the ship and crew...