For simple cake baking operation that is the norm....all ingredients
should be at room temperature.
But....
Technically it is still feasible to use cold eggs or milk as long as
the other ingredients are warm enough . The critical thing is that the
finished batter temperature is still within the limit that allow the
leavening components to interact with each other.. A cold batter will
slow down the intial release of CO2 from the baking powder .
The main difficulty with using cold eggs is that it rakes time to
aerate it, but when its aerated at that conditions the foam is more
finer resulting in cakes of more uniform crumb grain than eggs used
at room temperature. Besides there is more tolerance to overbeating
with cold eggs thatn with eggs whipped at slightly temperature.(
room temperature to warm termperatures.
But with muffins wiher the mixing involved is not that strenous and
the resuting batter temperature change is not significant, it is best
to have all ingredients at romm temperature before use.
Roy