My cursory read of the Montana State Supreme Court's Western Tradition Partnership decision which challenges portions of Citizens United is that it actually challenges only a very small part of Citizens United. See also Western Tradition Partnership, Inc. v. Attorney General of Montana and this editorial in the Daily Interlake.
While I'm not an attorney, my read of the decision indicates that the corporate litigants objected to having to organize as a PAC in Montana and not being able to directly contribute to candidate races.
The Montana Supreme Court essentially ruled that forming a PAC is so easy in Montana that no corporation could claim that its speech was restricted by the requirements of doing so. Whereas, in Citizens United, the litigants claimed that organizing PACs at the Federal level was time consuming and honerous enough as to possibly hinder and limit their rights to free speech.
The Montana State Supreme Court does not seem to assert that corporations should not hold personhood rights nor does it assert that they shouldn't have rights to speech in campaigns. It simply upholds the state's rights to have some basic restrictions on how corporations speak in elections.
If the Supreme Court were to unexpectedly uphold the Montana State Supreme Court decision, it would not slow rampant funding of elections at the state and federal levels but it would only allow some basic state restrictions on the form of corporate speech and the level of transparency in corporate speech.
Seattle's proposed Initiative Measure 103 actually strips corporations of their personhood rights and makes it illegal for them to spend money on electoral campaigns. This parallels the Pittsburgh City Council ordinance stripping natural gas drilling corporations that seek to "frack" within the city limits of their personhood rights (see Section 5); the act passed unanimously.
While the Montana Court admits in dissent that it is duty-bound to uphold the Supreme Court's Citizens United ruling, Initiative Measure 103 will give Seattle voters an opportunity to write laws in their local community that define a democracy free of corporate personhood and elections free of corporate influence. This is a right granted to voters - but not Judges and Courts.
This is the kind of lawmaking powers citizens still have, the kind that can non-violently challenge federal precedents around corporate speech and lead to more dramatic shifts toward clean government.
The most interesting part of the Montana Court's ruling is the final dissenting opinion by Judge James C. Nelson. He essentially says he thinks the approach of his colleagues to send a message to the Supreme Court is foolish and poorly argued while admitting that all the states of the union are swimming in a sea of corruption brought on by corporate personhood and corporate speech in elections.