It seems in my area if you use a Dr in one of the three main healthcare companies in my area they all use MyChart. The blood lab is owned by the hospital so they also appear on MyChart. Mine are linked that any provider in any of those three systems can see your records. Doctors in private practice and the radiology group use different portals.
My father-in-law was able to give permission for my husband to have access to his MyChart. My husband gets a message when his dad has new test results or messages.