I don't think that is a consideration for the project. Their OEM partnership also includes supporting a current generation Snapdragon SoC which seems to feature an integrated modem.
>A component being on a separate chip is orthogonal to whether it's isolated. In order to be isolated, the drivers need to treat it as untrusted. If it has DMA access, that needs to be contained via IOMMU and the driver needs to treat the shared memory as untrusted, as it would do with data received another way.
The baseband hardware is not integrated the same way like other phones are.