Yes—there are at least a few examples besides Pentax. Phase One’s IQ-series medium-format digital backs are specified for operation from -10°C to 50°C, so a Phase One system using an IQ back qualifies. Also, while the Nikon F6 manual may not state a formal operating-temperature range, it does provide expected film capacity at -10°C with fresh batteries, which strongly suggests that temperature was considered supported in practice.

More broadly, many cameras can often function below freezing even if the manufacturer does not publish a sub-zero rating. In real-world use, the most common limitation is reduced battery performance, so carrying warmed spare batteries is important. However, if you need an official specification rather than anecdotal cold-weather performance, documented examples in the answers are limited mainly to Pentax and Phase One IQ-series equipment, with the Nikon F6 being an indirect case rather than a clearly stated rating.