There may be no existing, comprehensive central management of electrical demand from heat pumps but that doesn't mean there are no mechanisms whatsoever, because there are systems already for regulating AC demand. In our region of the US, residential customers can opt in to a system where the electric utility can remotely disable their air conditioning compressor during times of peak load, in exchange for discounts. There are agreements on how long that can remain in effect, which would probably have to be stricter for heating systems, and probably have other safeguards added. There are also non-centralized AC mechanisms through Nest thermostats, where they can pre-cool buildings early in the morning to spread load out more evenly during the day.
Maybe just as important, whether or not there is a centralized mechanism for dealing with it, utilities already have exactly the same load problem with AC in the summer and have more or less figured out how to deal with that. It may be different in places where AC is less widespread, but in most of the US I wouldn't expect heat pump load issues to be much of a problem in the winter.
