With the new 1" grooved stuff by victaulic I assume it would be easier. Regardless you can, but you have to cut out a section of pipe, put a nipple with 1" tee on one end and 1" union on the other end so the fitter can put it all back together.
How many sprinklers are going to be supplied from that 1" pipe now? You may have an issue with calcs at that point.