Crocuses in the Park

The next stage of spring has come to town. All over the town park crocuses are springing up.
They  are a lovely sight coming up out of the still brown grass on a typical April day. All the more so for being the first thing I noticed as I walked out of the library.
Many of the crocuses are in flowerbeds but just as many are popping out of the grass seemingly at random.
I wonder how they got there? Did guerilla gardeners slip them under the grass one autumn? Did mice or birds dig them up and drop  them elsewhere when they found they were inedible? Or were the municipal gardeners feeling creative one day?