If an IRA "blows up" under Code Section 408(e), the IRA owner is not liable for the 4975 excise tax. A strict reading of 4975 suggests (to me) that other disqualified persons who participated in the pt remain jointly and severally liable for the excise tax. On the other hand, if the IRA blows up under 408(e), it ceases to be treated as an IRA as of Jan. 1 of the year of the pt, so how could there be a 4975 liability if the account is not considered to be an IRA? Is anyone aware of any IRS authority on the issue of whether other disq. persons remain exposed to the 4975 excise tax?

You make a very logical point. The IRS could take the position, I suppose, that the account was as of the time of the PT yet an IRA, and that those disqualified persons are not absolved of the PT liability merely by operation of the other PT penalty, i.e. the account being stripped of its IRA status retro to January 1 of the year of the PT.
I'm not aware of any authority on the issue, but have never heard of the IRS attempting to impose any penalty except the stripping of IRA status from the account.

Look at p. 45, col 2 (at the bottom) of IRS Pub. 590 (http://www.irs.gov/pub/irs-pdf/p590.pdf), where it states what you would suspect based on the statutory language: loss of IRA status as of a specific date (but no PT excise tax) to the IRA owner or beneficiary who engages in an IRA PT (resulting, of course, in income tax and potential early distribution excise tax), and PT excise tax for any other person entering into a PT with an IRA.