Hi, sorry about the delay. Yes you can have supervisors from other universities. At my uni, you have to have 2 internal supervisors and no more than 5 with no other limits on external supervisors. I know someone who has 2 external supervisors (5 total) as part of a large collaboration with another uni. Though your second supervisor does not need to be an expert in your exact topic but could be in the same field or even just help you with a specific methodology.