I am not questioning you. You came here and posted a sort of confusing thread and you asked for help? I was giving you my input because I trap spay and neuter all the time. I have over a dozen cats and except for the newest arrivals all my cats are spayed and neutered.
You need to let the owner of the building know how important it is to get the mom cat spayed. Use the resouces found here www.savesamoa.org
and print them out and hand them to him to read. Saving this cat from future pregnancies, will prolong her life. Just click on resources then on spay and neuter and go from there. If mom is a true feral and you go after her kittens and she will be around, you may get scratched or bit. If you do not know what you are doing I just ask that you seek the help of someone in your area that does.