Typical tech week for an opera could involve 4 evening tech rehearsals give or take: a Piano Tech, a Piano Dress, an Orchestra Tech, and Orchestra (or Final) Dress. The daytime is generally reserved for a combination of set and lighting work notes (no SM needed) and cuing sessions (writing the light cues). The cast only shows up to the evening rehearsals. Often the ASMs are the bodies onstage during the lighting session while the SM, AD, Director are in the house. The SM has that opportunity to put the cues into her book (unless the LD has been able to provide a cue list in advance - it's not always possible) as they are written. The SM would also coordinate with the available crew to set the stage properly for each scene that is being lit. The evening rehearsals with cast tend to be all out efforts to get thru the piece, in the Piano Tech focus on the transitions, skip the arias if there's no blocking as needed to save time. Scene shifts would be tech-ed during the day as time is available. There often isn't time to spend on that in the evening - you may only have 3.5 hours minus breaks to get thru a 3 hour opera.....
You should have a good idea by the end of room rehearsals what the tech cues will be and can make preliminary Rail and Deck Sheets. Also Prop and Costume running paperwork should be done. Give the paperwork to the various crew heads before their first tech rehearsal so they have an idea what to expect. Obviously things may change a little or a lot during tech. If you're prepared with a starting place you'll be in fine shape going into tech. Also before tech week you can put cues and standbys in your book as much as is known. More helpful is to put in the Places calls (generally 5 min. before any entrance, not just top of the act), 5 min warns on the ends of acts and major shifts. If you have rules regarding breaks find the moments within the show when you might be able to, say, give the chorus a break while the long duet scene is going on.
Every company is going to be a little different and hopefully someone at the festival, a production manager, a tech director can tell you how that operation works.
Let me know if you have other questions.
Good luck!