Will I have a signal on the long train journeys (e.g., Almaty to Astana)?

Only intermittently. Train journeys in Kazakhstan can last many hours (or even days) and cross vast stretches of uninhabited steppe. You will have a strong signal when the train passes through towns or settlements, but you should expect long periods with no internet during the journey. We recommend downloading all your movies, music, or books before you board the train.