I can confirm that it died, I spoke directly with the emergency manager about it some time back, he confirmed that it suffered some kind of major failure and wasn't repairable. The new siren is a 135, apparently it isn't hooked in quite it. The 50 was already disposed of.
As for active units in the immediate metroplex, I know of four: Seagoville, Bedford, and two in Richland Hills (32.82116, -97.22729); (32.80429, -97.23014), which came from Euless in 2002 (
https://www.newspapers.com/clip/48633513/). If there's still a P-50 in Grand Prairie, well, you know something I don't!