There are some incentives, as Professor Heller points out for materials sharing. In part this happens informally. For the last year I have been assessing applications for exceptions and credit from studnts, for what they studied elsewhere. To do this I have to compare courses from around Australia and across thew world. It is remarkable how similar they are, at least in my discipline of computing. This should not be surprising, as they are all working from the same codified body of knowledge, and assessment requirements,. Academics meet to exchange ideas, and also professional bodies, nationally and internationally, meet to set accreditation standards. While universities each market programs claiming unique features, the courses are really much the same.
There are some multi-university arrangements already in place. The most successful is Open Universities Australia (OUA), offering courses from 22 universities. These are online courses offered globally. The consortium includes leading institutions, but they tend to not promote their OUA membership. OUA is like Fight Club: many universities belong to OUA, but they don't talk about it. It perhaps would cut across marketing strategies based on claims of uniqueness, and the benefits of a campus experience, if students realized they could get the same degree from the same institution online, with option of including courses from others.
Even without OUA there is scope for students to DIY a qualification. For my Graduate Certificate in Higher Education, I wanted to learn more about online learning. So I obtained permission from my supervisor to undertake two courses (half my program), at an affiliated university. However, the paperwork need to do this was daunting. So I bypassed it, instead simply enrolling in courses as a professional development (non-program) student at the second institution, paying with my credit card, and presenting my results at the first for credit. This avoided using the complex inter-institutional procedures.
The Australian Vocational Education system already has full mutual recognition, and recognition of prior learning. The definitions of all units of learning at all institutions, public, and private are publicly available in one national database. A student can apply units from any institution for a qualification at any other. They can also obtain credit for work experience or prior learning for any, or all, of a qualification (I got 80% of a Certificate IV in Training and Assessment this way). It is unlikely universities would accept such a rigid system (and would not have staff competent to implement it). But they could do it at a limited level in disciplines, such as computing, which already are internationally standardized.
Heller, R. F. (2023). Plan E for Education: open access to educational materials created in publicly funded universities.