Normally a wild bunny will be scared by a domestic, may even try and fight. (I recently saw an a very interesting video though of a domestic bunny interacting with a wild rabbit — The wild rabbit was clearly doing binkies though as a defensive move, – though if someone didn’t know it would look like playing.)
However, if a domestic bunny actually made friends and mated with a cottontail (if that is the wild rabbit you are talking about - I don’t know where you live) they will not produce offspring even if they mate. It is not genetically possible. (that includes Hares and Jack Rabbits too)
Are you absolutely sure that these “wild” bunnies are not “feral” domestic? If it was a feral domestic, your bunny could be pregnant.
Some of the signs you may see would be nesting: pulling out fur of her own dewlap along with other soft things around and making a bed/nest. Some females can get feisty and extra territorial during this time as well. (This can also happen though with a false pregancy)
At about two weeks a vet or experienced rabbit person with should be able to feel for babies. I am not experienced as much with baby care as we focus here on non-breeding House Rabbits. For more information though check out these links:
Pregnancy/Babies – Uh Oh, Surprise Litter?:
Edited to ADD: I found that video I was talking about –
http://www.youtube.com/watch?v=6NMU-pKFBsU The domestic rabbit may be playing but that wild rabbit is just not sure what to make of this goofy funny domestic bunny.