I've been reading quite a bit about this whole case and unfortunately the more I read and discover, the more unnerving it is. I lived in Allen for over 20 years, so this case is one I can relate to as I read about all of the locations, and even people that I see are friends with other people mentioned on social media. I was browsing around a fb page called "You Know You grew up in Allen, TX when..." and came across a post referring to tunnels in Allen. The OP called them The Trip Tunnels" aand said there was "like a car down there." Another poster said "acid playground being built." They explained that these were like abandoned sewer tunnels that they would go exploring in because you could go "around the whole city." They said there were entrances by Ford and Bethany Lakes and Chapparal. (Ford is a middle school and also a city park, and Bethany Lakes is a park as well.) I had never heard of these tunnels, but then again I'm a bit older than these posters and certainly wasn't looking for an "acid playground."
The really disturbing part (if the tunnels are not enough) is that the original poster is one of Christina's friends on fb. It just seems that the more I research, the more shady people I turn up within her circle: people with arrest records for group 2 controlled substance (ie heroin), or sexual assault, or this tunnel hangout. It's as if they are all intertwined somehow and it makes me wonder what the story is.
I think this tunnel information warrants a tip to the Tipline. Especially given the person who posted it. You can submit a tip anonymously through the Plano PD website and they'll forward it on. May be nothing, but may be everything.