One of the sticking points has been the WRU seeking a stake in the four professional sides, with the governing body preparing to take on the Covid loan debt from the Welsh government.
That originally totalled £20m with Cardiff, Dragons, Scarlets and Ospreys initially saddled with the repayments.
Regional fans have concerns about the WRU being involved directly in each team's business, with fears the governing body would seek further control.
Tierney confirmed publicly the WRU is seeking some official input into the regions, but says her organisation are not trying to take over.
"It's been one of the things that has rightly made the clubs cautious in this process," said Tierney.
"The collaboration interest we are seeking are in terms of squad composition, minutes played and set-ups.
"This isn't a takeover or moving to the Irish model. We need to collaborate on a system that will give us the outcomes we need and benefit the regional clubs and national team."
And Tierney dismisses headlines claiming that would amount to Gatland running the clubs.
"It's important the four clubs remain independent and have their ability to be entrepreneurial.
"Hopefully fans see what it means in practice and won't be worried about the WRU."
Tierney says regional budgets are due to rise gradually next season from this campaign's sum of £4.5m, with the squads having a spend of around £6.5m a season in three years' time.
The chief executive also reaffirmed the WRU commitment to keeping four professional sides in Wales and that the prospect of an Anglo-Welsh league was currently off the table, saying English clubs had voted against the proposal.