Yes they have.
Widespread occurrence of a domestic dog mitochondrial DNA haplotype in southeastern US coyotes.
http://www.ncbi.nlm.nih.gov/pubmed/12535104
*But*:
“The widespread distribution of this haplotype from Florida to West Virginia suggests that the hybridization event occurred long ago before the southeastern USA was colonized by coyotes.
However, it could have occurred in the southeastern USA before the main front of coyotes arrived in the area _between male coyotes released for sport_ and _a local domestic dog_.”
There *are* morons intentionally breeding ‘coydogs’ for pets.
The article also says “closely related to” domestic dogs.
That’s a pretty big genetic spread in a very old study.
They’re just now admitting the wolf ancestry, after denying it for decades,