We can see the impact of fossil fuel lobbying. In fact, every single time the federal government has put forward any kind of climate policy, it's been attacked and then watered down by fossil fuel lobbyists, so there's a track record that clearly shows the influence of these meetings.
Of course, these lobbyists would not be spending hundreds of hours each year having meeting after meeting if they did not think it had an effect. If you meet with someone five times a day, you are going to be susceptible to their point of view.
Clearly, there is an influence by these lobbyists. It's also why the fossil fuel lobbyists and executives show up in droves at international climate negotiations as well. They're there to weaken climate progress, just as they've been doing for the last four decades.