That's a very interesting question. In theory, yes*, but how much "hidden" subsidy there is is another matter!
*Apart from the ones which are subsidised. Wien-Bregenz for one, I believe, as it links the western end of Austria with the more populous east through some of the more remote areas. And excellent value on an Interrail pass too, can be had for eur6 in the seats, and about eur25 in one of the new mini cabins! (Unless prices have changed since this summer.)
The economics of continental operations are very different to the UK. They still have "national" freight operators, who may (or may not) be notionally independent from the passenger side of the business, which immediately makes things easier in terms of contracting your sleeper haulage. Then, many (most?) electric locomotives have the necessary electricity supply kit for passenger stock. There are staff at key points who do shunting for freight, who can just pop over to the station for the sleeper then go back to freight in the yard etc.
Sleeper traffic is almost interchangeable with freight - simply hook up whatever locomotive you have spare at the start, and away you go. No need for expensive dedicated sleeper locomotives, which sit idle during the day.
Other advantages over on the continent are the different approach to route knowledge, and as alluded to above pretty much any driver who signs a suitable locomotive type can in theory drive the service (freight last night, sleeper tonight, freight again tomorrow, etc). Much simpler
All these problems can be solved. Diesel tanker lorry with hose pipe and an inflatable swimming pool (I don't know exactly what the requirements are, but these are found on construction sites where fuelling happens to catch any fuel spillages. And yes, it wouldn't be an actual swimming pool!). Train cleaners can presumably be anyone - making beds, vacuuming, emptying bins shouldn't require any specialist knowledge (and if it does, something has gone wrong). Toilet emptying tanker lorry with hose pipe and suitable attachment sorts the toilet issue. Staff can learn the route, especially if it's going to be a regular journey. Not a big problem.