GM has been strangely silent on this one.
Resistive heating vs heat pump is a BIG deal. And waste heat recovery should also be implemented. Toyota has gone with a "vapor injected" heat pump on the Prius Prime to keep it working in sub-zero temperatures, but there are other versions of heat pumps that also do that.
Heat pump BEV's are the LEAF, i3, Soul EV, e-Golf (SEL only), and upcoming Hyundai IONIQ.
Tesla S/X use waste heat recovery (from the drive motor and electronics) that can be used to heat the cabin and/or battery pack. Additional heat is provided by resistive heating. At the launch of the Model 3, some unspecified "special" HVAC features were touted but not revealed.
The REx version of the i3 has resistive heating - probably because the ICE can/does generate lots of waste heat.
The SE (low cost) version of the e-Golf lost the heat pump (as well as Quick Charging, 7.2 kW L2, leatherette seats/trim, LED headlights, larger touchscreen with navigation, & a few other odds & ends).
The Spark EV uses resistive heating as does the Volt (which also fires the ICE at very low temps, even with a full charge), so a heat pump on the Bolt would be a first for GM.
The lack of information on heating is not encouraging. A heat pump and waste heat recapture are things that GM definitely would brag about, so the silence implies they are not part of the Bolt design.