Of course. That's why SLC provides services to other RSPS...

Of course. That's why SLC provides services to other RSPS wholesale NBN backhaul. ABB doesn't need it to sell NBN services, but they are going that way because it will mean that their margins (long term) will be far more sustainable. That's why it's an interesting change in direction for them as most smaller RSPs own no fibre and buy capacity if and when they need them and thread the needle of competition, margin pressure, cost of acquisition of customers etc to keep running a viable business. Many would love to have a fibre network but often don't have the financial ability or the technical team there to implement in. ABB have been looking at IPO'ing so that they have access to capital markets to help fund some of these growth ventures. Now isn't a great time of course, and many argue that staying private has it's advantages and using other forms of funding.

Also ABB aren't building the backhaul only for NBN services, by having L2 connectivity into those DCs it allows better packaged solutions for medium to large businesses who may require L2 connectivity between key buildings (DCs, office buildings) but have remote offices serviced with NBN co and they can provide an all in one solution much like what Superloop, Vocus, Telstra, TPG etc already do.