The conference seeks agreement / negotiates with the network to plus up the compensation to UConn so that the rest aren’t diluted. The Network agrees if they see the value.
This may be the most important point. From media reports, the Big 12 basketball coaches want to add UConn, but the Big 12 more football-centric athletic departments currently don't see significant value in adding UConn (from a revenue or perceived quality of football perspective). The school presidents will probably not add a school unless such move is, at a minimum, revenue neutral for the existing schools at day one, and with the prospect of higher revenues in the future. UConn is probably only in the conversation because of its basketball teams and the Big 12 commissioner's stated objective to capitalize on his conference's basketball strength, and the potential to expand that strength into a national footprint (to generate more revenue for the schools). While not the driver like football, conference basketball telecasts and the NCAA Basketball Tournament are revenue generators, and with more consolidation of schools into the power conferences, the money will potentially flow moreso to the power conferences (that can leverage negotiating strength from both football and basketball) in the future.
There's also been media reports that when new schools join a conference, their share of revenue starts at a lower level and then increases over time in some type of stepped up formula. In order for something to happen, the starting amount of revenue initially shared with the new school might need to be the amount that keeps revenue neutral for the existing schools while covering the increased costs (for travel, etc.) for the new school and also increasing in a stepped fashion over time. Hopefully, such a mutually beneficial share amount exists for both sides because the networks are in control of how the revenue numbers are projected.
Simultaneously while the revenue numbers are looked at, media reports indicate some of the Big 12 schools have the same geographic and culture arguments against an invitation to UConn that have been discussed from UConn's perspective on this forum. But foremost, from each side's perspective, there must be a prospect for more increased revenue in the future.