Tell me though: for major, presumably border town rail stations, would it be the same ATM dispensing both Euros and CHFs or separate machines? ">
Could be either or both.
Look for Credit Suisse, UBS, Zürich Kantonal Bank, maybe Raiffeisen banks' machines. I picked bigger and more common ones, which are more likely to give you choices.
<<"If separate ATMS, how would I tell the
currency of the ATM before transacting?">>
After you put in your card and are recognized, there is a menu which tells you what you can do. If you don't find what you want, cancel and look for another machine. Some ATM's have a printed sign on them saying that you can get Euros, or that they offer small bills.
<<"We enter Switzerland at Geneva CFF and naturally want CHFs assuming Euros not widely accepted thru-out Switzerland, especially for small purchases. ">>
Geneva is very cosmopolitan. You'll find every possibility without much effort. Only some of the machines offer Japanese or Arabic instructions, however. ;-)
Switzerland aims to be tourist friendly, so that you will find Euros accepted at many places. The exchange rate may be an approximation of what you can get at the banks machines; for example, a restaurant prices in CHF, but does its own conversion if you pay in Euros.
In big cities such as geneva, many menus or price tags show both currencies.
<<"Good to know I can designate the denomination at an ATM.">>
Often, not always. More common at big city machines.