OK
Confession time.
I ordered new rims and spokes for my A twin, from a supplier from whom I had previously ordered spokes and rims. The rear from the first set had broken a couple of spokes but had been fine since they had been replaced, which I mentioned to the supplier.
When the new set arrived, they were set up for cross 3 lacing, and not cross 4. I was outraged, phoned the man and told him so. He said he had done so as he presumed they previous ones had broken because of the interference as A_HRD has mentioned above, which did not appear to be the case. Surely said I, a note of an e mail or a quick phone call could have ascertained my preference. The response of course was to send them back and he would replace them with cross 4 bits. All well and fine to say but by the time one has paid the freight to the west coast of Canada, and the tax on the import (no duty but 12% VAT, plus a "handling fee") and then paid to return them, and then pay more tax (which may or may not be added as they are replacements) and freight again and "handling fee", it becomes a very costly effort. Sooooooooooooo I suck it up and go to replace my rims. I had not taken the wheels apart yet, and when I do attack what appears by any investigation to be the original from the factory, it is laced cross3!!!!!!!! Really??? Yup really.
So they are laced cross 3, and if they are set up for cross 3, of course it can be done.