It's not just the shore. I am involved in similar projects in urban/suburban areas and they almost consistently miss their mark. Honestly it's not a bad thing because the way these projects go, if you give people (both customers and vendors) a far out date they will slack off longer thinking they have more time whereas people do their best to hit a date so they will prioritize better and make informed decisions about pushing back deployments.
The larger the more likely delays. Shore systems probably slip mostly because these are big changes for small counties. In Worcester County's case, it sounds like - as is the case many places - they tried to keep costs down and then found out they needed more towers... this seems to be a common theme these days... we're seeing new systems require double (or more) the number of towers.
It's always better to delay and get it right - unlike some other western shore counties did by only building half a system and going live.
There could be other reasons for delays too. I know of a new P25 system near me that was essential "forced" to go live because - as the story goes - the old Motorola system suddenly "failed"...
It was interesting to see the numerous failures of the Upper Shore (UES) system just before they switched over to FiRST... gotta wonder.
I've heard rumors that several counties in Maryland have had to push back new systems including Montgomery, Anne Arundel, and Howard for different reasons.
Ha! These three haven't much gotten off the ground at all. Lots of paperwork, etc. and in some cases, funding for planning and other things seems to constantly get shifted to other priorities.