No, it is not used in France. But "pomponné" and "pimpant" are so close phonetically and semantically that they might have merged into "pimponner". Well, I suppose so... But the word may be of another origin, or it may simply be an evolution of its pronunciation in Louisiana. The DLF does not say anything about it.
And yes, French fire trucks and police cars go "piiin pooon, piiin pooon", and ambulances go "pin pon pin"
My granny who lived in moreauville & spoke cajun french all the time. She came to live with us in New Orleans as she got up in age. She used that word to describe me all the time because I was always looking in the mirror fixing my hair & makeup (and often made us late going anywhere)! .