That was my thought. I wonder would the OP expect to spend yuan renminbi in a TVM in Hong Kong?
Not normally so, but the ticket office can deal with that.
The ticket machines at the high speed station only accept Hong Kong dollars and only sell tickets on its own line, but there are also some ticket offices which accept Yuan Renminbi, operated by the central Chinese operator (with a booking fee applied), selling tickets for the whole national network including the cross-border trains, while for bus travel from Macao to Hong Kong, 3 currencies are accepted to buy the ticket.
There are also ticket collection machines by the Chinese operator, which was put by popular demand, as the MTR-operated machines can't be used to correct tickets bought from the Chinese operator.
There are also opposite examples as well - tickets for coach travel between Hong Kong and mainland China can only be bought in the currency of the departure region, however both singles and returns are available.
In Copenhagen Airport, beside the main ticket machines, there are also separate machines, by DSB selling only tickets to Sweden, and by SJ selling tickets in the whole Swedish network, but none of them accept cash and they are not used by anyone there.
I was actually expecting that Danish money are used to buy tickets to Copenhagen, and Swedish money are used to buy tickets to Malmö, as the airport is a border station.