My wife just recorded my dogs reacting to your dogs lol

Our border collie would never howl.  Not at police car sirens, not at fire truck sirens, not even with the two mixed breed bird dogs in the pen with her howled at the sirens or anything else.

The two boys would sit there, look at each other and when the first one tossed his head back to howl the other one would, then they'd just go at it.  But the border collie (female) would be going about her business, whether it was laying on the porch, getting something to eat, or walking around looking for a good place to use the bathroom.

I used to have a blue merle border collie that loved to howl, and if we humans would howl with him even for a short time, he thought it was the most wonderful thing in the world.  After a short time howling with him (his name was Skye), he would let out a giant sigh, and it was as if all the stress in his system had just been magically taken away.  I guess howling together is a pack bonding thing.

Every time I replay the vid he'll start howling.  It's awesome.  This was the first time I'd heard him howling this long and those yelps at the end.  He likes to howl some with his yawns too.
He won't howl with me though, I guess the pitch is wrong.

My in-laws have a Rott/Lab mix that howls when he hears sirens. Seems like a weird thing to do for the type of mutt that he is. Hilarious none the less.