Since 9/11 and this being a major public event with runners from around the world, it's reasonable to see the use of such dogs or even drills, no?
Or maybe there was a report of terror activity. Of course anything else could also be and we'd never be told about it.
Before you read the “Outside The Lines” report, consider this:
Taping the opposing team’s sideline still isn’t banned; only taping the opposing team from the sideline is illegal.
Also remember this:
Taping the opposing team from the sideline wasn’t banned until 2006, yet the report cites examples as far back as 2000. ~NESN