I don't know any firmwares for the BCD325P2 or the 15X.
But about OpenScanner for BCD and SDS models : this firmware allows you to, yes, *hear* the encrypted trafic, but let's bring the precision that it is the *garbled* kind of noise of encrypted traffic that is "hearable".
This is like the Whistlers scanners that offer the choice of hearing this garbled sound, or a busy sound, or silence, on E traffic (as you know Unidens just skip over E traffic).
I did try OpenScanner, but i regret it as it messed up big time my BCD436. it was not a positive experiment; I reverted back to Uniden firmware, but the scanner is still slow and unreliable.
So, if i can recommend, be very careful with "alternate" firmwares, if there's ever one for the BCD325P2 or 15X. A Whistler scanner may be a better choice for you.