There are multiple types of "cedar" none of which, BTW, are true Cedar in the US, except some ornamentals planted in the Southwest. The three common types of Cedar are Eastern Red-Cedar Juniperous virginaina) which is common in the eastern 2/3 of the country and it is the wood that is commonly used for pet shavings. It is also the on you want most to avoid. The chemical oils in it that keep moths away, aren't terribly good for mammals either. The other main Cedars are Thuja plicata (Western Red-Cedar) a tan to pinkish colored wood which is commonly used in cedar shakes (shingles) and Thuja occidentalis (eastern Canada) which is also used for lumber.
I don't like wood shavings for rabbits, but that is just a personal opinion. I suspect shavings made out of the two "Thuja" species are no more harmful than any softwood or pine shavings, but those made from the Juniper species (darker red and light chips) with the "cedar chest" odor, should not be used except in an emergency.
True cedars are native to the Mediterranean and Middle East and belong to the genus "Cedrus"