Ttraffic rights are indeed not transferable, but the point is that when you split a company which owns route rights, there are no rules as to which part should have what rights; there is no rule that says each part must have an equal share of the traffic richts. in short, you can split in 2 parts, one having all the good things like the lots, traffic rights, etc. etc. and one having only the depts.
That's what they did at SR and also what is now going on at SN.
It is not easy, but it is not impossible eighter.