According to a driver I spoke with yesterday, he said that ABQ RIDE is currently testing a few CNG buses. While I haven't seen them, he said the buses are 40-footers and have a front end like the 700s/900s/6900s, so I am guessing they are New Flyer C40LFRs. Perhaps they could be the replacement for the 300s.
I find this quite interesting. Perhaps ABQ RIDE wants to have a little variety in the fleet, and maybe doesn't want to entirely abandon CNG as a fuel. Of course, don't count on any CNG buses for the Rapid Ride, as there is no space to park articulated buses at the Yale Transit Facility, and the Daytona Transit Facility doesn't have any CNG fueling capabilities.
Of course, ABQ RIDE will have to tender out a new contract for bids if they want to buy new CNG buses. In addition to the New Flyer C40LFR, other options include the North American Bus Industries (NABI) 40-LFW CNG and the Orion VII NG CNG. Gillig is out of the question as they don't make CNG buses. There is also a fourth option (the ElDorado National Axess), however, since there are no large scale operators of the model, I don't see ABQ RIDE taking a risk with a model without a proven track record of reliability and durability.