Earlier this month a prisoner (Patrick James Buswell) escaped from Stillwater Correctional Facility in Minnesota, he just walked right out of the prison in broad daylight! Mistakes happen everywhere. (http://www.fox21online.com/news/local-news/Stillwater-Prison-Escapee-Caught/33629988)
Also, I highly doubt that it's just "business as usual" at Clinton right now - if hoisting lunch were something abnormal, it wouldn't be happening at this time, not with the spotlight they're operating under. I think the simplest explanation is likely correct: it's difficult or cumbersome to get lunch from the tower, so they use a hoist system.
A prison allows workers to leave their post and take lunch breaks. It is a serious security breach for anything to be hoisted from outside a maximum security prison.
JMO