In general, a good passage is page 194 of DtD: "Pacts and Other Creatures of the Night"
This passage implies that other supernatural types are treated as normal mortals in regards to pacts. Ergo, it makes sense to say that, since mortals have no "inherent advantage" to detecting pact-based changes, and supernaturals are treated largely the same in regards to pacts, it is logical that supernaturals would have no inherent advantage.
From another angle, page 122 details the Clash of Wills, emphasis mine:
Sometimes, two supernatural powers oppose one another.
From the description of pacts, page 189, emphasis mine:
All demons can forge pacts, and this ability does keep more than a few demon philosophers awake at night.
Two pages later:
When a contract is destroyed, the pact is immediately nullified.
So, in this sense, Demon have the ability to anchor changes in reality in the form of Pacts; this is a differentiation from their powers to passively or actively alter reality (with Embeds and Exploits, respectively.)
Now, it could be argued that Mages (because of their resonance with different realities) might have some advantage to track down changes to reality (through Fate spells or somesuch) but I am not familiar enough with them to know of something offhand.
For the specific example of a Demon masquerading as the Vampire Prince and doing a gender swap, that would be a very disadvantageous situation. First, in order to gain praxis, the demon would have to convince a Prince to either sign away his soul or his praxis; and, in the case of a soul pact, the passage on 194 details that the Demon would take aggravated damage, and the resultant cover would be a normal mortal, unable to pass for a Vampire.
Now, assuming the Demon had Deep Cover from Flowers of Hell, they could spoof as a Vampire - bearing in mind it'd be a roll for every scene, with a dicepool of 10 or less. Add to that, that Deep Cover just provides protection from detection attempts. Assuming the Demon has Show of Power, that's an Exploit - every time the fake Prince needs to demonstrate his Celerity or Majesty, you're running risk of Compromise - and that's not even taking into account that Show of Power is contested.
But, the circumstances that drove a Demon into such a precarious situation certainly sound intriguing, to say the least.