While slanted towards public safety, the above link does have good info.
Snipped from that link...
What This Means To Users
All existing Part 90 radio systems operating on frequencies between 150-512 MHz have eight years to convert those systems either to 12.5 kHz bandwidth or to a technology that provides one voice path per 12.5 kHz of bandwidth or provides a data rate of 4800 bps/6.25 kHz.
12.5 kHz Conversion Deadline for Existing VHF/UHF Systems
* Industrial/Business Pool licensees conversion deadline remains January 1, 2013
* Public Safety Pool licensees conversion deadline has been changed to January 1, 2013
* After this date, all systems must have converted either to 12.5 kHz bandwidth or to a technology that provides one voice channel per 12.5 kHz or operates at a data rate 4800 bps per 6.25 kHz of bandwidth.
Basic Questions & Answers
Q - Are we forced to move to 800 MHz?
A - No. Narrowbanding does not require moving to another frequency band.
Q - Will we have to buy new radios?
A - Depends. Most radios purchased in the last 6-8 years are already narrowband capable. They only need to be re-tuned.
Q – Will we need to change frequencies?
A – No. You merely reduce the bandwidth of the channel(s) you are now using.
Q – Will that reduce our coverage?
A – Little if any. You may have to survey your system and area of operation. Only a thorough analysis of your coverage requirements can tell for sure.
Q – Will we have to convert to digital?
A– No. However, many agencies are using this opportunity to upgrade to digital technology. Most digital radios are dual mode capable and can operate in wide band analog as well as narrowband analog and digital. Digital is also more immune from adjacent channel interference along with features unavailable in analog.
