In PHX, leads can either be "hired-on" permanent leads or lead-qualified agents that can be temporarily upgraded.
Agents that are "upgraded" to Lead for a shift automatically have their pay increased for that shift as well, it shows up in Workbrain as a pay differential for that day. If an agent is upgraded in the middle or end of his shift, he (is supposed to) receive lead pay for the whole shift. Only agents with "quals", or team lead qualifications, can be upgraded or pick up lead shifts. Once you're qualified, the only way to become unqualified is either sign up to have your qualifications dropped with management (which they rarely allow) or get on a level three disciplinary level. I know of a few leads that either have or were considering getting on a level three just to lose their lead qualifications.
Agents that are qualified to be leads and are not "hired-on" dedicated leads may at the beginning of a new bid period sign the "no pull" list which basically puts them towards the bottom of the upgrade list. A lot if not most lead qualified agents sign the no-pull list but in a pinch they'll still upgrade people from it anyway.
This problem used to be more severe until a couple of years ago when PHX was effectively opened for transfers and furloughs to come to be leads, in fact becoming a FT dedicated lead was the only way a lot of those people were able to make it to PHX. Before that time easily half the leads on the ramp for a given shift were upgrades. Even though they had a slew of hired-on lead positions filled since that time, management has never stopped relying on the flexibility that comes with being able to upgrade certain agents at will.
A lead may get an ESON for something amiss at his or her gate, such as the main gear not being chocked, or a missing delineator or what have you since they are responsible for that gate; in fact if they wanted to they could give the whole gate crew ESON's for no one having noticed it or done anything about it. A lead won't and shouldn't receive an ESON when an agent on the crew is neglecting something that that agent is personally responsible for or his doing with his person; for example if Johnny Idiot is hopping between carts and over tongues his lead isn't going to get the ESON for it, Johnny is.
Leads do not issue ESON's in PHX, never have. Hope this clarifies...