Either of the two would come up with say $143m for 25% of the...

Either of the two would come up with say $143m for 25% of the Hillside project (not RXM shares but the company that holds the Hillside leases.)

RXM then has to raise 854*.75* 0.35=$224 for it's part of the equity of the Hillside project to get it built. The other 65% is debt financed.
But it already has $143M from the sale of 30% of the project so it only needs $81m.
This is raised by a combination of forward sales of concentrate (streaming)* and and equity raise say $35m = $50m*0.75 plus the rest an equity raise of $41 m form insto's and current Sh. Note the SP of the equity raise will be higher than now because the plan for financing will be all laid out and agreed and the market knows it's not some huge raising just $46 m a spit in the bucket for insto's especially since a lot want will be taken by current SH at a discount. Maybe a rights issue.

The JV partner has to come up with funds it's share of the 35% of equity before debt on it's 25% in the project.

Not the Hog ranch project would be excluded and to the extent RXM want's to raise more funds from project sale streaming or cap raise for safety factor & to progress that it can.

The junior partner has rights to it's 25% of revenue or possibly concentrate and geos along happily till. The project expands or it wants to go predatory. Which will be dependent on the success of the project.

Note some time after the project is up an running the manager will want to renegotiate debt to bring the interest rate down which it can because it's a lot less risk now.

All IMVHO.
* actually the concentrate sales agreement is the first cab of the rank before the JV.