I believe the battery cooling system on that Escape is nothing more than a fan. The previous gen actually had liquid cooling. That's because it was using off the shelf round D cells. Ford switched to a square, prismatic cell like Toyota uses. These cells are much more efficient at dissipating heat.
Whatever cooling system used, it's there to keep the battery from cooking itself during the summer. The cold of winter only reduces its efficiency. So a heating system isn't in place since there is always the ICE to move the vehicle. The heat the batteries generate isn't enough to overcome freezing temps.
There is a fan, with an a/c evaporator coil. In cool temps it will draw outside air to cool the battery pack, but when the outside air is too warm, it will cool the air with the a/c system. If you look under my Escape, you can see the freon lines running under the vehicle. I think in 09 they did away with the a/c system cooling the battery in favor of another method.
The gen2 and later Prius just has a fan to circulate cabin air into the battery compartment. Blocking the vent on the side off the rear seat, or hauling hairy dogs, can cause problems. The gen1 drew in outside air. The vent on the C-pillar is one way to tell it from an Echo.
Engineers didn't bother trying to warm the battery. Only people like us would appreciate the gains in cold weather. Most of the public wouldn't notice. So it wasn't worth the effort.
How accessible is the battery compartment from inside the cabin? Perhaps a small 12 volt heater or blanket could help warm the battery if that's the issue.
It is likely the battery being too cold. Hybrids tend to have a larger percentage drop in fuel economy than a standard car with the cold. Still do better in total numbers. I only bothered with a grill block, and still got around 45mpg in the winter with the Prius.
Trying to heat the battery is an option to try if the WAI and grill block aren't enough.
Ok, today I programmed the Scangauge to display battery temp as a gauge. Started today with a 29F battery. After a couple short stops I had it to 70F. It seems that the battery warms up just fine with use. I think any attempt to try to warm it up faster with a 12V blanket or other means would just waste more energy than it saves.