I think there are pretty specific circumstances under which this is allowed, not just for any NW DC family who wants to opt out of Wilson. For example, people who have come from overseas to work in their country’s embassy here in DC, or for the World Bank or whatever, and happen to be living in MoCo. This is the case actually with a family on my block — they are just renting here for a few years, and are attached to their country’s diplomatic corps, and as such I don’t think they are paying taxes in MoCo. These provisions allow such families to attend the local schools despite not being taxpaying residents, as long as they pay.
Here is a link - this is handled within MoCo’s International Admissions and Enrollment Office, which is an indicator of the purpose of the program:
https://www2.montgomeryschoolsmd.org/departments/studentservices/schooling/faq/
In any case, it’s subject to having space at the school in question. BCC is over capacity.