Christie,
I'm presuming these were seedlings? If so, they're all a different 'variety', and will cross-pollenize one another.
I don't have any personal experience with sandcherry(is that P.besseyi, or something else?), but yes, they're edible. Tasty may be another matter altogether.

They are Prunus x cistena
Would they all be purple if they had been grown from seed? I assumed they were all clones of each other. Maybe not.
They were all just covered with blooms. I wonder why I don't get more cherries.

Yes, they could all be purple. In order to be clones of one another, they'd have to be grafted selections or root suckers from the same plant. I suspect that the utility co. is probably giving out seedlings, which could probably be obtained in large quantities for not much $$.
You didn't say exactly how old they are, but they may just need to gain a little more 'age' to begin bearing more heavily. I've got some Chickasaw(P.angustifolia) and beach(P.maritima) plum seedlings that have been growing 5-6 years or more, and this is the first year they've produced more than just a handful of fruits.

I don't remember when I planted them. Is that a sign of old age? More than 5 years ago and less than 10. The fruits are marble size or maybe slightly larger. I've read they are "short lived". They better hurry and start making fruit.
Does anyone else have a lot of cherries on their purple-leaf sandcherries?

High Country Gardens has a new Sand Cherry (Prunus besseyi) they call 'Select Spreader'. Sounds like a really good one. I would have gotten it if I ordered from them this year. I used up my budget ordering from other places this spring. But I did order more Nanking Cherries. I also learned that Sand Cherries, Choke cherries and Nanking Cherries are supposed to pollinate each other.

I am thinking that the Purple leafed Sand Cherries don't commonly make fruit, just pretty flowers. Like ornamental flowering Cherry trees that don't make cherries. Of course the Sand Cherries are grown for the purple leaves.

I have 4 Cistena Plum Trees (Sandcherry) and does anyone know what the cherries taste like? Are they more bitter or sweet?

Mike

I had a total of zero cherries on my sandcherries this year and I'm still determined to get them to fruit. The University of Connecticut site says prunus x cistena is a "hybrid between P. pumila and P. cerasifera 'Autropurpurea'"
What should that tell me? Would a different hybrid such as 'Big Sis' work best to pollinate them or would either of those two species work just as well?
Mike - you asked about the flavor. They were sour but not bitter and tasted ok. Not as sour as a pie cherry to me but not as sweet as a big cherry. I'm sure there are better fruit trees but since I already have them, I'm hoping I can get them to do something.
On the downside - the juice is pretty dark and looks like it could be bad to stain.

I intended to add this link because it listed a couple of cultivars.

Here is a link that might be useful: Prunus x cistena at UConn

This is the first year my Sand Cherry has had fruit. I planted it about 5 years ago and assumed it was a flower-only plant. The fruit is good and tastes like plums. Not sharp, not really sweet either, but good. There were about 100 cherries. Pits like regular tree cherries, and darker red. YUM.