I'm not overly familiar with how these deals work. Certainly no more than your average fan. Few thoughts though.
SURELY prior to going though a costly tender process the SPFL will have a rough idea how much other channels could have within budgets/have an interest in the rights/what they're likely to bid.
If another broadcaster was genuinely interested without question the minute they heard about the potential sky deal they'd be in contact with the SPFL making them aware of their interest even if it was an "off the record" type offer and conversation. If that happened and it was worth more money, this sky TV deal wouldn't be going anywhere - that's a certainty.
I can't see them simply pushing forward with this deal without at least having a reasonable understanding of what the likelihood of other bids are and their potential financial level.
In the same way you don't just simply go through a costly tender process without some level of confidence that another offer will come in higher than what's already on the table. Otherwise it's a waste of time, resources and potentially results in the eventual deal being lower than what's already being offered.
I know the SPFL aren't the most savvy organisation sometimes but it's not as simple as they've jumped at the offer without at least some due diligence going into it. Other club directors WILL have asked about this. Some of these people are very successful business men.
There was also articles this morning suggesting Rangers were doing this, because they wanted an apology over the Cinch fall out was there not?