I think it's important to remember that the police department does not owe us or the media one spec of truth - they aren't under oath. Anything they offer up could be a half-truth and I feel like they are keeping a LOT close to the vest - including not filling the family in on things. An example of this is the cameras - for all any of us know - all 3 cameras could have been in good working condition and they know what cars are on the film. They know and reasonably have access to everything we've discussed here - toll tag records, camera, cell phone pings. It is a wealthy community with lots of resources, tax base, etc. They have the resources to take care of this.
Regarding keeping everything close to the vest, it's important to remember that many of Christina's friends (and her siblings friends) are young, in college/just out of college and they talk - a lot - in person and via social media. The PD has to be concerned about leaked information making its way out to the potential perps and the general public.
Being from the area, I have a lot of confidence in the abilities of the Plano PD. JMO, but I think they know a LOT and may be just giving the perp enough rope to hang himself. If she is indeed no longer with us, having the recovery (alive or not) by Texas Equusearch would be the final touch on the investigation.
Reference the recent Erin Corwin case in California - little to no information from the PD, people criticized them for not doing enough and letting the accused go back to Alaska. A few (long) weeks later, they recovered her body and promptly arrested the accused.
I'm going to choose to have faith that the PPD and TxEq are a lot closer to solving this than we think.