The accuracy of published papers varies dramatically and can not be assumed. Specifically in the case of IEEE, it's a huge organization with lots of conferences and journals. Some of them tend to be more strict about what they accept than others. Some of the papers I've read from IEEE made me wonder whether they went through any peer review process at all, as the language wasn't even comprehensible. Even in the most respected journals and conferences, though, results should not be assumed accurate. You should use your own judgment to evaluate the logic and arguments presented (i.e. to ensure that their conclusions really do follow from their premises/experimental results and that their experimental designs seem reasonable) and, where feasible, repeat the experiments to verify their results.
At any rate, the peer-review process that papers go through for publication is not a verification of the results, even in the most respected journals. The peer-review process consists of other authors looking over the paper and pointing out any perceived weaknesses in the arguments presented, noticeably incorrect results (i.e. math errors and the like,) and/or formatting and language errors. In some cases (especially for more general conferences,) the reviewer isn't even in the same research field as the paper (e.g. an RF engineer might be reviewing a paper on power systems or an AI researcher might be reviewing a paper on computer networks.) IEEE publishing a paper is basically saying "After a cursory review, one or more members of IEEE think that this paper doesn't appear to be complete trash and likely has some academic value to someone," not "IEEE asserts on the basis of its reputation that this paper's results are correct."
The process you seem to have in mind - other researchers repeating the experiments to verify the results - is a completely distinct process from the peer-review process required for publication. This process usually doesn't start until after the paper is published. This is generally true for all scientific publication, not just IEEE. Mathematics is something of an exception in that they attempt to present actual proofs rather than scientific results in their papers. That is also often the case in the algorithms and logic side of Computer Science. Even in those fields, though, you should check the proofs yourself, not assume them to be accurate just because they got published.
Especially where it is not feasible to reproduce a paper's results yourself, it is perfectly acceptable to cite that paper's results in your paper as a comparison. You just need to make sure that you cite it as something along the lines of "<authors of other paper> found that their system achieved X performance level, while our experiments show that our system achieves Y performance level." That way, it's clear that you're not claiming to have verified their results, but that you're merely comparing what you saw from your system to what they claim to have seen from theirs. Of course, if it's actually feasible for you to test the other system yourself and present your own experimental results for it, that's better.