Have some similarities but my opinion: these are not Portulaca oleracea.
Rather I agree with Paul, Portulaca umbraticola, but how he said is need to see the seeds capsule to be sure.
The plants in photos above are somewhat different from those which I saw until now in the wild in Texas.
Maybe they are a cultivar of Portulaca umbraticola variety/subspecies from South America.
Here
http://australianportulaca.blo...
a very interesting article, which bring some explanations about the misapplied names for the cultivars ‘Wildfire Mixed’.
The South America's origin of these cultivars are mentioned in Flora of North America, here:
http://www.efloras.org/florata...
