It would probably do so by advocating against the policy in the public forum where their employees weren't specifically targeted as the audience.
I think the meat of the issue is that Uber doesn't get to decide Prop-22, it's a decision by California and if you want to sway CA talk to CA. If you legitimately think your business and all it gives to the economy and community would be destroyed by that proposition then tell that to all the residents of the state - targeted messaging to your employees is just all sorts of shady and, whether intended or not, it will leverage the power imbalance of the employer/employee relationship for some people.
It's pretty much the same reason you should look elsewhere for love - there is an existing relationship between an employer and employee - bringing other relationships into the scenario just makes things murky.
Well, your idea actually produces an effect counter to what I would assume your preferences are:
Large employers, with a lot of market power would still be able to communicate to their employees via public channels. Small employers with very little (employment) market power would be basically muted.
It's better than what we have now - I think the US needs to take a very serious look at purchased speech in the long run but there are a whole bunch of problems we'd need to solve for that and I've been told by the PM that that's out of scope for this project ;P
I think the meat of the issue is that Uber doesn't get to decide Prop-22, it's a decision by California and if you want to sway CA talk to CA. If you legitimately think your business and all it gives to the economy and community would be destroyed by that proposition then tell that to all the residents of the state - targeted messaging to your employees is just all sorts of shady and, whether intended or not, it will leverage the power imbalance of the employer/employee relationship for some people.
It's pretty much the same reason you should look elsewhere for love - there is an existing relationship between an employer and employee - bringing other relationships into the scenario just makes things murky.