This is an old video from Deir Al-Zoor and it says in Arabic 'Caliphate army mobilizing to assist Deir Al-zoor'. Not from Raqqa. Citing Al-Masdar propaganda website should be enough to know how credible is this.
But looking at the map, it seems like Deir Al-zoor is more or less where they said the convoy went. (Sections of convoy later spotted here)
Saying "mobilizing to assist Deir Al-zoor" sounds better (on a IS point of view) than "evacuating Raqqah".