Labrat, Gene and others have already covered most of this, but I thought I would throw my hat in the ring!
As has been reported, the basement of Amistad appears to be a large animal facility housing rodents for research studies. The facility would be shared by many investigators, and is most likely subdivided into "suites". Anton Bennett's mice possibly occupied one or two suites.
There would also be seperate "procedure rooms". In Annie's case, given that she was working on diabetes, this is where she would take her mice to do such experiments as monitoring blood glucose etc.
The animal facility is staffed by superivsors and animal/lab techs. There are also vet/vet techs that rotate through all the univerity animal facilities. The animal/lab techs look after the rodents on a day-to-day basis. They change, food/water, monitor general animal well bieing, cage overcrowding etc. It is a tough job, and not particularly glamorous.
Lab/animal techs are usually assigned to particular suites, so it is more than likely that Annie interacted with the same person/tech on a regular basis. The lab techs listed on the Bennett homepage are different to these lab/animal techs. While the Bennett lab techs may be involved in animal studies - like Annie, they would travel back and forth from Amistad to their actual lab space. By contrast, the lab/animal techs spend all of their time in the animal facility. It is not clear who the media are actually referring to. In fact, given the facility is shared by multiple investigators, the "lab tech" referred to in the media could be from another research lab all together. It really is impossible to tell.
From what I have read, Annie had recently decided on her PhD thesis topic. This suggests that she was early in her graduate career, and had probably been working in the Bennett lab for less that 6 months.
With this is mind, it seems surprising that she would make an impression on a lab/animal tech in such a short time - but certainly not impossible. Come to think of it, if her project was heavily reliant on mouse studies, she could be spending several hours per day in the animal facility. It is unlikely that she would see or interact with the lab/animal tech outside the animal facility - the techs are usually finished by 4-5pm, while Annie sounds like she typically worked late.
The animal facilities will have large autoclaves for sterilizing waste as well as large racks of rodent cages/bedding prior to use. Certainly large enough for an adult human. I can't imagine what would happen if you autoclaved a body, but it may explain why an autopsy was required to positively identify the body. I am worried that if autocalving was involved, forensic evidence may be compromised.
As someone else pointed out, autoclaving a body may generate a large amount of extra steam due to the body containing a lot of water. This may have overwhelmed the built-in exhaust system, and triggered the alarm. Once the animal facility was emptied of staff, the suspect would have ample time to dispose of the body in the manner described. This link mentions strategies to deal with the generation of liquid (steam?) when autoclaving animal carcasses.
http://tempico.gostrategic.com/dynamic.php?pg=Applications/Infectious
Let's hope that authorities can make an arrest shortly. RIP Annie Le.