In a group interview with Raider.IO and Icy-Veins, Blizzard has confirmed that the first Matrix Catalyst charge will be available when Season 1 starts with Heroic raid week on September 10th, gaining an additional charge every 2 weeks!
Group Interview with Icy-VeinsGroup Interview with Raider.IO
In other words, this means you'll get a tier-converting catalyst charge on week 1, 3, 5, etc. No word yet on exactly when Crafting Sparks will become available or if they will overlap with this two-week cadence though. Interestingly, this question and answer are not present in Raider.IO's writeup of the same group interview, so we encourage readers to check out both for more questions and answers.