Well from memory Intel sold off the general purpose ARM CPU division to Marvell back in 2006 or so. Though it kept the ARM chips that were specialised for storage or networking IIRC. So technically Intel has always made ARM chips in one form or another, just not any that slot into a mobile phone.
Based on what another commented has said it seems Intel bought the ARM license from DEC, and given that they sold off only the consumer ARM chips - keeping the task specific ones - it makes sense in a way. It was so they wouldn't have any internal competition or divided focus away from their low power x86 chips - the Atom's.
Which makes articles like this one: http://www.digitaltrends.com/computing/intel-arm-processors-... ridiculous.
"the unthinkable happened. Intel revealed it was going to build ARM processors."
Do your damn research, people :-)