Where to begin? Firstly, they've taken the Climate Change Commission's budget (which had already been weakened) and weakened it further, giving themselves an additional two million tons of pollution in the 2022-25 period. The "justification" for this is that the latest Afforestation and Deforestation Intentions Survey showed that "landowners and forest managers [plan] to increase afforestation and decrease deforestation". That's right - they're planning to raise the budget because people are planting too many trees and soaking up too much carbon.
There is a very weak argument here. Yes, forests have lower soil carbon than grassland (however, they have much, much higher above-ground carbon). How much? The numbers are in table 6.3.2 of the 2019 Greenhouse Gas Inventory. The difference, which will be released over a number of years, is 14 tons / hectare. If we ignore the fact that this will be compensated entirely within the first three years of growth, and apply that number to the government's budget increase of two million tons means it would allow over 140,000 hectares of afforestation. How much extra afforestation does the survey project in the first five years? Looking at the table on p9, and subtracting off the Climate Commission's baseline of 25,400 hectares a year [p72] gives a total of 26,200 hectares. So even if we accept their "afforestation is bad!" argument and count only one side of the ledger while ignoring the other - which we shouldn't - their numbers don't add up. They're giving themselves five times as much carbon as they need! (Alternatively, they're ignoring the Climate Commission's base case, which means their numbers still don't add up).
Another point worth noting here is that forest owners aren't the only people with intentions. This year the Tasman Mill - 250,000 tons of pollution a year - has closed, while the Marsden Point oil refinery has announced plans to shut down. The Emissions Reduction Plan (footnote, p 12) estimates the impact of that at 2.5 million tons of carbon over the first budget period, which combined with the million tons over four years from the Tasman Mill more than offsets any piffling concerns about soil carbon from trees. But like I said, they're looking at one side of the ledger but not the other. The over-riding concern here I think is to give themselves a high first budget so it will be met, so they can declare the policy a success. But the overall impact is to abandon ambition and push the problem out and leave it for future governments. Which is what they've done all along.
Secondly, as has been widely reported, the plan basicly ignores agriculture. This is our biggest source of pollution, and a source of methane, a gas we need to cut immediately to limit heating. And the government's "plan" for doing this is to rely on the He Waka Eke Noa partnership (which is all about delaying action), and of course that old staple "research" (which is also about delaying action). There are real policies they could pursue here: stocking limits, a shrinking cap on cow numbers (enabled by data from the NAIT system), even limiting low-value dairy exports. Instead, they're just going to let them keep on polluting as if there is no problem, while the rest of the country pays for it. And that alone means it is not a credible plan.
There are apparently some good suggestions in there for transport, but given the above issues, there seems little point in engaging with them. We cannot reduce our emissions unless we do something about agriculture. As long as we continue to ignore the giant cow in the room, then we will continue to fail.