Trying to understand your question.
1) You are in a state that requires collaboration or supervision
2) Your physician/physicians does/do not want to cover you for writing controlled substances despite being granted the privilege by your state
3) There is some confusion about how to write this script for a patient.
1) You cannot be stopped from obtaining a DEA certification, unless your state requires your collaborating/supervising physician to authorize your ability to prescribe. In Florida, I don't have to have an authorization to prescribe issued by the state. After January 1, 2016, I will be able to apply for the DEA certification on the DEA website, and pay $731 for 3 years.
2) Your collaborating/supervising physician can grant you whatever scope of practice they will grant you. They are in charge of what they will cover you for. That is on your agreement with them, and is usually sent to the state BON for record-keeping. For example. I have 3 different supervising physicians for 3 different jobs that I do. Each is different, with regards to what they will cover me for. I will have a DEA number, but I can't use my DEA number to prescribe pain medications to patients I visit for wound care. That physician has decided we don't need that in our scope of practice.
3) "if this Rx is signed by x, x , or x (which are NP in the group practice) it is authorized by the MD." If I understand this correctly, they are telling you to sign these scripts, and granting authorization to you. They can't do that. Either you have a DEA number, and write the script within the bounds of the state requirements for you as the prescriber, or you write it out, and they sign it under their bounds as a prescriber. Be careful with pre-signed scripts, because using them will send you to jail.
Hope this helps.