Portland Public Safety is in the VERY early planning stages of upgrading their radio system since the existing system is failing. When the system is upgraded it will be digital, however it is highly unlikely that it will be encrypted. This means that current local listeners will be required to buy the more expensive digital capable scanners to continue listening.
This upgrade is part of a complete overhaul of Portland Regional Communications Center's technology system and will include a new CAD system as well. As with any project, money is going to be the primary issue which will require that it is completed in stages. Due to the current status of the project, I would not worry about buying a digital scanner within the next year or two. However....it would be wise to start saving money if you do not already have one. South Portland Fire/Police purchased digital capable 800mhz radios when they switched from VHF a few years ago, so they will be ready to swap when Portland eventually makes the switch. Portland on the other hand will need to upgrade many, if not all of their 800mhz mobiles and portables during overhaul. So...it is a very large project that will at least take a few years to fully implement.
Also, if a department is using a P25 system, it does not automatically mean they are implementing encryption. Very few departments in the US actually implement encryption. I know of only three or four police departments in Vermont that do and many of the federal government agencies as well. It just may sound that way to those who have analog scanners since digital signals will sound all garbled.
KB1VLA is correct. The "Scarborough 800mhz system" does not actually exist and has been in the RR database for years. I do not remember what the reasoning was for that, but for some reason I remember someone saying that they have the licenses for those 800mhz frequencies, but do not use them.