Had severe dysplasia (had leep), now breakthough bleeding. Any connection with precancerous cells of the uterus and cervical dysplasia?

It is unlikely that. Your irregular bleeding is related to the leep or utrine cancer unless the leep was recently done and u r bleeding from there. Cervical cancer and uterine cancer are seperate phenomenon, though cervical cancer can extend into the uterus. Depending on age, uterine cancer is low on the list as a cause of the bleeding but see your doc if older than 35, may need endometrial biopsy just 2 b sure?
No, IF.... Assuming you are healed from the leep, then there is no relationship between these two processes. Dysplasia is an anatomic abnormality of the cells of the cervix caused (usually) by a virus. Breakthrough bleeding is a functional abnormality of the uterine lining often caused by hormonal issues. However, there are some anatomic problems that can cause bleeding, so you should check with your gyn.
Dysplasia. 95 % of cervical abnormalities are of the surface layer (squamous epithelium). The smaller portion is of the glandular tissue. If your dyplasia was not glandular in nature, then no connection with precancerous cells of the uterus.