brakes and cold weather

Hey all,
I'm not sure if anyone out there has experienced a 'squirting' type sound upon pressing the brakes when the car has been parked for >24hrs in <10degF climate. This has happened to me twice in big bear, no change in braking performance, but it sounds really strange, and it's REALLY loud, people outside the car can hear it quite well, especially when stealthing. The last time this happened, I was able to get all the way back to the 22 with the noise still there (that's about ~180 mi, of course I got kick butt mileage on the return trip ) The weather below the mountain was something like 60degF, so I'm pretty sure that 180mi of that should have warmed anything that was frozen up. Additional observations:

It happened whenever you depress the brakes starting from zero. even zero to <10% (even if you're just regenerating (what limited energy you can regen when the Ilimit is +77A (ermm, the battery WAS at +49degF!)) Took like 30mins to get the battery toasty (+93degF) too! --this part is normal, or if it isn't, it SHOULD be normal.

The squirting sound did not continue to happen as you went from 10% to 100% pressure. (you can hear the PWM valve kick in at this point.) --not sure what toyota calls this valve.

There was no correlation between the brake accumulator pump cycles and the squirting noise.

I tried preheating the pads several times to see if it was in the caliper/rotor. Based on kinetic energy math, going from 55-35 several times, this should be enough, right? (using the neutral trick to get the brakes warm.)

I've noticed this twice in very my car is parked in very cold big bear winter conditions (well, cold for me, anyways. )

In any case, if anyone else has heard this, what is it? If it's a bad thing, what got replaced?

Also (probably unrelated, but pretty disconcerting.)
Today, while stuck in rush hour traffic, the brake accumulator pump started cycling on about once every 10 seconds or so, it kept doing that for almost 15 minutes. I was not riding the brakes too much, just enough to maximize regen. What's weird was that it continued even for periods of good stealth areas. Foot was NOT on brake, brake position readback as 0%, throttle position was read back as 0-10% (human invoked EV mode.)

I'm not sure what is causing either one of these, if there's anything I should be looking at, I would really appreciate the info.

Regards,
_echo